Paying a Premium for High Octane Gasoline? | Consumer Information Paying a Premium for High Octane Gasoline? Related Items Report Labeling Problems ﻿ Read Your Owner’s Manual Unless your engine is knocking, buying higher octane gasoline is a waste of money. Premium gas costs 15 to 20 cents per gallon more than regular. That can add up to $100 or more a year in extra costs. Studies indicate that altogether, drivers may be spending hundreds of millions of dollars each year for higher octane gas than they need. It may seem like buying higher octane “premium” gas is like giving your car a treat, or boosting its performance. But take note: the recommended gasoline for most cars is regular octane. In fact, in most cases, using a higher octane gasoline than your owner's manual recommends offers absolutely no benefit. It won't make your car perform better, go faster, get better mileage, or run cleaner. Your best bet: listen to your owner's manual. The only time you might need to switch to a higher octane level is if your car engine knocks when you use the recommended fuel. This happens to a small percentage of cars. ﻿ About Octane Ratings What are octane ratings?

Octane ratings measure a gasoline's ability to resist engine knock — a rattling or pinging sound that results from premature ignition of the compressed fuel-air mixture in one or more cylinders. Most gas stations offer three octane grades: regular (usually 87 octane), mid-grade (usually 89 octane), and premium (usually 92 or 93). The ratings are posted on bright yellow stickers on each gas pump. What's the right octane level for your car? Check your owner's manual. Regular octane is recommended for most cars. However, some cars with high compression engines, like sports cars and certain luxury cars, need mid-grade or premium gasoline to prevent knocking. How can you tell if you're using the right octane level? Listen to your car's engine. If it doesn't knock when you use the recommended octane, you're using the right grade of gasoline. Will higher octane gasoline clean your engine better? No, as a rule, high octane gasoline doesn’t outperform regular octane in preventing engine deposits from forming, in removing them, or in cleaning your car's engine. In fact, the U.S.

Environmental Protection Agency requires that all octane grades of all brands of gasoline contain engine cleaning detergent additives to protect against the build-up of harmful levels of engine deposits during the expected life of your car. Should you ever switch to a higher octane gasoline? A few car engines may knock or ping even if you use the recommended octane. If this happens, try switching to the next highest octane grade. In many cases, switching to the mid-grade or premium-grade gasoline will eliminate the knock. If the knocking or pinging continues after one or two fill-ups, you may need a tune-up or some other repair. After that work is done, go back to the lowest octane grade at which your engine runs without knocking. Will knocking harm my engine? Occasional light knocking or pinging won't harm your engine, and doesn't mean you need a higher octane. But a heavy or persistent knock can lead to engine damage. Is all "premium" or "regular" gasoline the same? The octane rating of gas labeled "premium" or "regular" isn’t the same across the country. One state may require a minimum octane rating of 92 for all premium gasoline, while another may allow 90 octane to be called premium.

To make sure you know what you're buying, check the octane rating on the yellow sticker on the gas pump. ﻿ Report Labeling Problems If you don't see a yellow octane sticker on a gasoline pump, file a complaint with the FTC. The FTC enforces the Fuel Rating Rule, designed to ensure producers and marketers give you the information you need at the pump. Octane ratings: Difference Engine: Who needs premium? | The Economist Tweet EVEN at the cheapest petrol station in your correspondent's neighborhood, filling up the family kidmobile with premium (91 octane) fuel now costs over $70. As the meter clocks up dizzying dollar amounts, he looks longingly at the regular (87 octane) pump. Switching from his vehicle’s recommended premium-grade fuel to the cheaper variety would lower his fuel bill by at least 20 cents a gallon (more than five cents a litre). The question is, would it be worth it? On the surface, the decision appears easy. Because the name “premium” implies a souped-up fuel that packs an extra punch, many motorists actually believe it delivers more oomph or miles per gallon—and may therefore represent good value.

The truth, however, is that premium contains no more energy than regular petrol—around 114,000 British Thermal Units per gallon, depending on the season, the region, the local pollution requirements, and the amount of bio-ethanol that has to be added to petrol in America by law to keep the country’s corn-growers in clover (see “ Competition at the pump ”, August 20th 2012). The difference between premium and regular petrol lies in the blend of hydrocarbons used to make the fuel, and the package of additives mixed into it. Nowadays, petrol is made up of hydrocarbons (mainly paraffins, naphthenes and olefins) produced in a catalytic cracker or reformer. The refinery process breaks the crude oil’s large hydrocarbon molecules into smaller ones by vaporising them in the presence of a powdered catalyst (an absorbent mineral such as zeolite). The blend varies depending on where the crude came from, the refinery equipment used, and the grade of petrol being produced. Additives are included to reduce carbon build-up inside the engine, improve combustion, inhibit corrosion and allow easier starting in cold climates.

Fuels that meet the requirements for “Top Tier Detergent Gasolines” (a voluntary standard endorsed by BMW, General Motors, Honda, Toyota and Volkswagen) contain more detergent in their additive packages than the minimum required by the authorities. Another key additive that blenders stir into their brew is ethanol. That is done these days primarily to boost the fuel’s octane rating. A higher octane rating allows an engine to use a compression ratio of, say, 12-to-one instead of a more usual ten-to-one. The greater the compression, the higher the temperature within the combustion chamber. And the higher the temperature, the greater the thermal efficiency and power produced. In a nutshell, high-compression engines designed for performance need high-octane petrol. Though ethanol has less energy per gallon than petrol, it has a considerably higher research octane number (RON)—around 108 to premium’s 97. It should be noted that this is not the octane rating seen on the pump in America. The RON figure results from a laboratory test done using a special engine with a variable compression ratio.

In the fuel test, the compression is raised until the engine begins to “knock”—ie, the fuel in the cylinder ceases to burn smoothly and instead detonates before it can be ignited by the spark plug. The cylinder pressure at which this occurs is then compared with that achieved while the engine is running on a reference fuel (a mixture of iso-octane and n-heptane). The ratio of the two pressures provides the RON of the fuel in question. A better way of measuring a fuel’s ability to resist knocking under load is the so-called motor octane number (MON) test. This uses a similar test engine, but with a preheated fuel mixture, a higher engine speed and variable ignition timing. Because it uses more real-world conditions, the MON rating is typically eight to ten points lower than the equivalent RON figure. In Europe, the octane rating on the pump is simply the RON figure. America, by contrast, uses the average of the RON and the MON figures, called the AKI (anti-knock index). Thus, 97 octane “super unleaded” in Britain is roughly equivalent to 91 octane premium in the United States.

Whatever the test, the point is that knocking needs to be avoided at all cost. If allowed to continue, it can quickly cause an engine to disintegrate. That is because when the air-fuel mixture in the cylinder detonates spontaneously before reaching the top of its compression stroke, the rising piston confronts a wall of rapidly expanding gases from the explosion, which attempt to force the piston back down the cylinder. The stresses caused by suddenly trying to reverse the rotation of the engine can become high enough to shatter the pistons, connecting rods and parts of the crankshaft. To prevent that happening, a high-compression engine uses a blend of hydrocarbons that is somewhat less combustible than normal. Ethanol has an auto-ignition temperature of 362ºC, while petrol bursts into flames without a spark between 246ºC and 280ºC, depending on the blend. Therefore, adding a little ethanol to petrol can raise the auto-ignition temperature enough to prevent the blend from igniting purely from the heat generated during compression. On the face of it, then, a motorist would seem ill-advised to use regular petrol in a car with a high-compression engine.

That was certainly the case in the past. But cars today have sensors that listen carefully for the knocking sound, and instantly retard the ignition system when they detect that detonation is about to happen. The delay in delivering the retarded spark allows the piston to start moving downward on its expansion stroke before the ignition actually occurs. That provides additional room in the cylinder head for the gases to expand and thereby reduce their damaging peak pressure—and so burn in a more controlled manner. To sum up, if the car’s handbook says that premium petrol is “recommended” (rather than insisting it is “required”), then the engine will automatically adjust itself to run smoothly on a lower octane fuel. Because of the retarded ignition, the engine will, of course, produce less power, and have slightly higher fuel consumption. But the poorer fuel economy is likely to be outweighed by the savings at the pump. Even so, your correspondent remains reluctant to make the switch. One reason is that no one has been able to tell him what damage is done, if any, by running the engine permanently in a retarded state, and forcing the anti-knock system to remain active all the time. Another reason is because all the vehicle’s emissions testing was done using the recommended grade of fuel.

Despite the fact that modern fuel-injection systems adjust the air-fuel mixture for changing conditions, your correspondent still has no idea how much more pollution the car might dump into the atmosphere if he switched to regular. Premium certainly has a better additive package, which helps keep the tailpipe clean as well as the inside of the engine. But his biggest reason for sticking with premium, though, is that he was well aware that the car needed 91 octane to work properly when he bought it. And having paid upfront for the higher performance, he is reluctant now to throw that benefit away. As for those who earnestly believe (and quite a few do) that filling the family Toyota with premium will somehow make it go faster or deliver more miles to the gallon, all one can say is don’t bother. As one wit noted, the only thing it will make run faster is money from your pocket. Selecting the Right Octane Fuel Selecting the Right Octane Fuel Selecting the Right Octane Fuel What is octane rating? Octane rating is the measure of a fuel's ability to resist "knocking" or "pinging" during combustion, caused by the air/fuel mixture detonating prematurely in the engine.

In the U.S., unleaded gasoline typically has octane ratings of 87 (regular), 88–90 (midgrade), and 91–94 (premium). Gasoline with an octane rating of 85 is available in some high-elevation areas of the U.S. (more about that below ). The octane rating is prominently displayed in large black numbers on a yellow background on gasoline pumps. What octane fuel should I use in my vehicle? You should use the octane rating required for your vehicle by the manufacturer. So, check your owner's manual. Most gasoline vehicles are designed to run on 87 octane, but others are designed to use higher octane fuel. Why do some manufacturers require or recommend the use of higher octane gasoline? Higher octane fuels are often required or recommended for engines that use a higher compression ratio and/or use supercharging or turbocharging to force more air into the engine. Increasing pressure in the cylinder allows an engine to extract more mechanical energy from a given air/fuel mixture but requires higher octane fuel to keep the mixture from pre-detonating. In these engines, high octane fuel will improve performance and fuel economy.

What if I use a lower octane fuel than required for my vehicle? Using a lower octane fuel than required can cause the engine to run poorly and can damage the engine and emissions control system over time. It may also void your warranty. In older vehicles, the engine can make an audible "knocking" or "pinging" sound. Many newer vehicles can adjust the spark timing to reduce knock, but engine power and fuel economy will still suffer. Will using a higher octane fuel than required improve fuel economy or performance? It depends. For most vehicles, higher octane fuel may improve performance and gas mileage and reduce carbon dioxide (CO2) emissions by a few percent during severe duty operation, such as towing a trailer or carrying heavy loads, especially in hot weather. However, under normal driving conditions, you may get little to no benefit. Why does higher octane fuel cost more? The fuel components that boost octane are generally more expensive to produce. Is higher octane fuel worth the extra cost? If your vehicle requires midgrade or premium fuel, absolutely. If your owner's manual says your vehicle doesn't require premium but says that your vehicle will run better on higher octane fuel, it's really up to you.

The cost increase is typically higher than the fuel savings. However, lowering CO2 emissions and decreasing petroleum usage by even a small amount may be more important than cost to some consumers. What is 85 octane, and is it safe to use in my vehicle? The sale of 85 octane fuel was originally allowed in high-elevation regions—where the barometric pressure is lower —because it was cheaper and because most carbureted engines tolerated it fairly well. This is not true for modern gasoline engines. So, unless you have an older vehicle with a carbureted engine , you should use the manufacturer-recommended fuel for your vehicle, even where 85 octane fuel is available. Can ethanol boost gasoline's octane rating? Yes. Ethanol has a much higher octane rating (about 109) than gasoline. Refiners usually blend ethanol with gasoline to help boost its octane rating—most gasoline in the U.S. contains up to 10% ethanol. Blends of up to 15% ethanol are available in some areas, and several manufacturers approve using this blend in recent-model vehicles. The Straight Dope: What's the difference between premium and regular gas?

What's the difference between premium and regular gas? October 8, 2004 Dear Cecil: In this time of high gasoline prices, the Teeming Millions need your guidance (well, at least I do). What is the difference between premium and regular gas, and is this difference worth the extra money? I normally put premium gas into my car because I don't mind paying two or three extra dollars at the pump. Am I being scammed by the gas stations, or is the benefit to my car worth it? — Jeff, via e-mail Not to introduce a radical concept, Jeff, but have you tried reading your owner's manual? If it says to use premium, my advice is to use premium. If it says regular, use regular. The fact that your note indicates no acquaintance with such matters suggests that you may in fact be a scam victim, assuming by this you mean "someone who believes what he hears in commercials." I have a hard time working up much outrage over this deception, since discovering the facts requires so little effort. If you don't mind paying the extra money for no reason, don't expect the oil companies to suffer any pangs accepting it.

In most of the U.S., regular gas has an octane rating of 87, midgrade gas is 89, and premium is 91 or 92. (Octane ratings are lower in the mountain west due to the effects of thin air on internal combustion.) Contrary to widespread belief, the octane rating doesn't indicate how much power the fuel delivers; all grades of gasoline contain roughly the same amount of heat energy. Rather, a higher octane rating means the fuel is less likely to cause your engine to knock or ping. Knock, also known as detonation, occurs when part of the fuel-air mixture in one or more of your car's cylinders ignites spontaneously due to compression, independent of the combustion initiated by the spark plug. (The ideal gas law tells us that a gas heats up when compressed.) Instead of a controlled burn, you get what amounts to an explosion--not a good thing for your engine. To avoid this, high-octane gas is formulated to burn slower than regular, making it less likely to ignite without benefit of spark. The majority of cars are designed to run on regular gas, and that's what the manuals tell the owners to use.

Higher-performance cars often require midgrade or premium gas because their engines are designed for higher compression (higher compression = more power), and regular gas may cause knock. If your car needs high-octane gas, the manual will say so. Using high-octane gas in a car designed for regular accomplishes little except more rapid combustion of your money. Some refuse to believe this, claiming, for example, that premium gives the family Toyota better mileage or more power. These people are in dreamland. Others say premium is purer or contains detergents that will cleanse your engine of uncouth deposits. Likewise misguided thinking--government regulations require detergents in all grades of gasoline. (BP Amoco, I notice, asserts that its premium gasoline contains more detergents than legally required; if you think that's worth 20 extra cents a gallon, be my guest.) Some automotive types claim that using premium in a car designed for regular will make the engine dirtier--something about deposits on the back side of the intake valves. I've also heard that slower-burning high-octane gas produces less power when used in ordinary cars.

Believe what you like; the point is, don't assume "premium" means "better." Occasionally you get some genius who takes the opposite tack--he spends an extra 10 or 20 grand buying a high-performance car, then decides he's going to save three bucks per tankful using regular instead of premium as specified. He figures as long as the engine doesn't knock he's OK. Wrong, carbon monoxide brain. Car engines nowadays contain knock sensors that detect detonation and automatically retard the spark to compensate. The delay means maximum gas expansion occurs when the piston is farther along in its downstroke and thus there's more room in the cylinder head. This reduces peak cylinder pressure, eliminating knock but also giving you less power and poorer mileage. You may ask: Don't knock sensors make it hard to tell when an old car needs higher-octane gas? Years ago, when your beater started pinging on grades or under acceleration, that was the sign that carbon had built up in the cylinders, increasing compression, and it was time to switch to high-test. Now the knock sensors compensate, which seemingly might conceal the problem.

Don't fret--today's fuel injection systems precisely meter the fuel-air mix, resulting in fewer unburned hydrocarbons and less carbon buildup. If you're still concerned, I'd say it makes more sense to spend $6 on a bottle of carbon clean-out juice than an extra $150 a year on high-priced gas. — Cecil Adams Unleaded Gasoline - Premium and Regular Gas | Exxon and Mobil Introducing Exxon and Mobil SynergyTM Gasoline Engineered with 7 key ingredients, working together for better gas mileage.** Meet the team: Fuel Detergent 1 – helps provide excellent protection against intake valve deposits in traditional PFI (Port Fuel Injector) injection engines Fuel Detergent 2 - helps provide Intake Valve Deposit protection for PFI engines and also provides additional protection for modern Direct Injection engines.

Cleaner engine parts can lead to better gas mileage Anti-Adhesion Compound - helps prevent fuel detergents from forming a sticky film on the intake valves; which in turn helps prevents cold start problems at cold temperatures Corrosion Inhibitor - helps prevent rust in fuel distribution system and/or key engine parts the fuel comes into contact with such as the gas tank and the intake valves Demulsifier - helps keep water from getting entrained in our additive in the distribution system. Helps prevent accumulation of water in your gas tank by allowing it to be separated and removed Solvent Fluid - enables the additive ingredients to stay mixed and to flow, and not freeze at very cold temperatures Marker Molecules - ensures we can determine the correct amount of our unique additive is added to our gasoline TOP TIER® SynergyTM gasoline – quality you can depend on When you fill up at an Exxon- or Mobil- branded stations, you can be confident you’re getting TOP TIER gasoline, every time. Available in three octane levels, our Synergy™ gasoline has been engineered with 7 key ingredients and developed to clean up intake valves, which help improve gas mileage and performance.* Exxon and Mobil SynergyTM gasoline grades Gasoline grades are based on octane ratings .

The higher the octane number the greater the fuel’s resistance to knocking or pinging during combustion. In most areas of the country our regular gasoline is 87 octane, midgrade is 89 and premium is 91 to 93. To determine which Synergy™ gasoline grade is best for your vehicle, check your owner’s manual. Exxon and Mobil Regular Gasoline Octane 87 Our regular grade unleaded gasoline was developed to meet the needs of most vehicles in America and is our most popular gasoline. Exxon Plus and Mobil Special Gasoline Octane 89 Our midgrade unleaded gasoline was developed to meet the needs of vehicles that can benefit from a higher octane, such as some sport vehicles and high performance cars. Exxon Supreme and Mobil Super+ Gasoline Octane 91–93 Our premium grade unleaded gasoline was formulated with a higher octane level and additional detergent additives to meet the demands of some of today’s most advanced engines. It generally has an octane level of 93 but is blended with an octane level of 91 or 92 in certain areas of the U.S. FAQs about gasoline Premium unneeded?

Octane rating explained How to drive a stick shift car Premium unneeded? Octane rating explained When pulling in to a gas station to fill up, we have a choice. Many of us don't even think about it and automatically choose regular gas, mainly because it's the most affordable. Whereas some of us will choose premium because we think it's better gas and therefore better for the engine. But is it really? For years, oil companies have been trying very hard to instill the "good, better, best" concept into our collective driver psyche with prominent ad campaigns and clever names for their premium gas. Is there any truth to their claims? It's a question that many people ask themselves and one that we're going to shed some light on. Octane Rating At every gas station, there are three types of fuel: regular, mid-grade and premium. Each is differentiated by its fuel octane rating, which is usually displayed at the pump. Regular gas has an octane rating of 87, mid-grade 89 and premium either 92 or 93. So what is an octane rating? It's a measurement unit that determines a fuel's resistance to combustion, or in simpler terms, how easily a fuel can burn.

The lower the number is, the easier the fuel will burn. All gasoline grades contain equal amounts of heat energy; it's the combustion level that varies. The octane number that you see at your local gas station is used in North America only. If you plan to do some driving in Europe, it's important to know that their octane measurement system, the international standard known as the RON (Research Octane Number), is 4 to 5 points higher than our pump octane rating. The fuel is the same but measured differently. As a comparison, regular fuel overseas would be 92, mid-grade would be 94 and premium would be 97. This is something useful to know to avoid confusion if you rent a European model car that has specific fuel requirements. That being said, higher octane does not necessarily mean higher quality, this is a common misconception. Higher octane number, with its greater resistance to combustion, is designed to help reduce engine knocking. Knock, Knock Commonly known as pinging or knocking because of the noise it makes, an engine knock is an uncontrolled spontaneous detonation of fuel occurring ahead of the sparkplug-initiated flame inside the cylinder.

This explosion occurs due to the fact that lower octane gas cannot withstand the compression that takes place inside the cylinder. When the combustion from the sparkplug and the spontaneous detonation collide, it makes a pinging noise and in more extreme cases, a knock. A small ping is annoying more than anything else, whereas a heavy knock, on the other hand, especially at high revs, can quickly destroy a piston. Higher octane fuel is designed to prevent pinging and knocking in the engine. The higher the octane rating, the more resistant a fuel is to this uncontrolled combustion. The more resistant a fuel is, the more the engine can compress it without it exploding. This is an important factor for high compression engines, or engines equipped with turbochargers, which are usually high performance sportscars or luxury cars. A high compression engine compresses the air-fuel mix very near to the detonation limit to produce more power and add to the overall performance of the vehicle, hence the need for higher octane number. Such cars with engines that require premium gas (91-92 octane) will very visibly indicate this requirement, either right on the speedometer, on any of the gauges or on the fuel cap itself.

Enter Technology Nowadays, to help counter the problem of engine knocking, cars are equipped with knock sensors. It's a small device bolted onto the engine block or cylinder head designed to record misfiring in the cylinders. When a knock or ping occurs inside a cylinder, the sensor generates a small electrical charge. In turn, this weak electrical signal is sent to the vehicle's ECM (Electronic Control Module), the car's onboard computer, and tells it to delay the firing of the spark in the combustion chamber. That way there wouldn't be two flame fronts igniting simultaneously in the cylinders and thus, the knock wouldn't occur. The ECM continues to keep a track of the signals sent by the knock sensor throughout the process, and brings the ignition timing of the engine back to normal once the knocking is completely eliminated. In cars with advanced or very powerful engines (V8, V10), more than one knock sensor is used, which makes the task of detecting engine knocking even easier. Safe to upgrade or downgrade? As its name implies, premium gas comes at a premium price, usually about 30 cents per gallon above the price of regular. Some carmakers recommend premium gas for certain models but do not place it as a requirement.

If premium is simply recommended, this merely states that this is the engine's optimal fuel. It will run on regular, although its potential for producing the intended horsepower and torque will be inferior. Should the engine begin to knock due to early detonation caused by the lower grade of gas, the ECM will adjust the fuel/air mixture and ignition timing to allow for less compression which will stop the knocking. However, this will consequently and inevitably lead to a loss of power. As for upgrading from regular to premium in a car designed for regular, in some cases, the engine may not run as well. This is because of the slower burn rate of higher octane fuel. Instead of the detonation occurring at the moment that it was set to, the fuel is ignited after the piston has already reached the top of its stroke, after the time the detonation was meant to occur, hence part of the explosion is wasted and so is the extra money you spent on premium. Also, since the higher octane fuel is not compressed enough before it is ignited, it may not completely burn in the combustion chamber of your engine. It would finish burning in your exhaust system where it does absolutely no good.

Moreover, many people will argue that higher octane number will yield better fuel economy, especially on cars with engines designed for regular gas. This is another popular myth. All gas grades contain roughly the same amount of heat energy, what the engine uses to generate mechanical power, and the octane rating has nothing to do with the amount of energy found in the fuel. What about mid-grade? At the halfway point between regular and premium is mid-grade. The added octane found in mid-grade is a 50-50 mix of regular and premium, blended directly at the pump. Some cars and trucks, very few, still require or recommend 89 octane gas, along with some motorcycles. This fuel type is especially popular and practical in regions of elevated altitude since a car's octane requirement will actually decrease with height due to the lower atmospheric pressure found at that level. At high altitude, because the air is thinner, there is less air in the air/fuel mix, there is less compression taking place and less pressure in the cylinders, so the fuel octane does not need to be as high.

As you increase in altitude, if you're driving in a mountain for example, or if you live in a mountain state, the fuel in your car is going to act like a higher octane than it really is. So an 89 octane may act like a 92 or 93, thereby eliminating the need to spend extra for premium for those whose cars require it. Is premium a cleaner fuel? Many people assume that premium is a cleaner fuel with fewer impurities than regular. This is also a myth. Federal regulations require detergents for each octane number. There are many additive packages that enhance the properties of gasoline. The detergents reduce carbon buildup, all the more important these days with high-pressure direct-injection hardware. Antioxidants improve storage and tank life. Corrosion inhibitors are also added. These are all systematically included in each octane number. It's generally suggested, and all oil companies will acknowledge, that their premium gas has more extensive additive packages. Our advice is to ignore their marketing tactics about the super-special detergents that they say come in their best fuel. Your engine will have sufficient protection regardless of the octane number you use. What does ethanol do?

For the past decade or so, you may have noticed that the regular and mid-grade pumps indicate a certain percentage of included ethanol. If you're like a lot of people, you may wonder: what is ethanol and how is it affecting the fuel you put in your car? Ethanol is a form of highly flammable alcohol derived mainly from corn and used as a biofuel additive in gasoline. It was implemented as an environmental measure as part of the Clean Air Act. It is used to oxygenate the gasoline mixture, which in turn allows the fuel to burn more thoroughly and therefore produce cleaner emissions. Currently, the vast majority of gas stations will have the ethanol additive blended at a minimum of around 6 percent while the pump stickers state "up to 10 percent ethanol". Its use in fuel has obvious benefits for air quality: ethanol blended gas can reduce a car's carbon monoxide emissions by up to 30 percent. It's also useful economically by helping to alleviate the global dependence on oil. Because of its oxygen and alcohol properties, ethanol also acts like an octane enhancer, standing itself at about 100 octane. It's because of this high number that it's not blended with the already high-octane premium gas.

However, the downside with ethanol is the fact that it has a much lower energy content than gasoline, about 30 percent less, which translates into fewer miles per gallon. The typical blend of roughly 90 percent gasoline and 10 percent ethanol, known as E10, has been approved in many countries and can be used with no modification to the vehicle's engine. Flex Fuel The proponents of ethanol see it as the fuel of tomorrow, the greener choice for the environment and the solution to foreign imported oil, as corn can be homegrown and in large quantities. Ethanol also has a lower per gallon price than gasoline, making it more affordable and more enticing to motorists. For these reasons, many carmakers have chosen to develop engines that can take an expanded percentage of ethanol-to-gasoline ratio, consisting of 85% ethanol with 15% gasoline, known as E85, or flex fuel. The lower pump cost of flex fuel is offset by the fact that ethanol is less fuel efficient than gasoline, as mentioned earlier, and also by the lack of availability of E85-equipped gas stations. Flex fuel requires a separate pump that will deliver the adequate blend.

There are currently only about 2,100 E85 stations across 44 states according to the U.S. Department of Energy. Unfortunately, this is but a mere fraction of the overall number of conventional non-E85 equipped gas stations. Flex fuel's intentions and potential are both good, but it still has many years to go before having the equivalent everyday convenience of traditional gasoline. So which to choose? After all is said and done, the simplest answer of which fuel to use is to follow the advice and octane recommendation contained in your owner's manual. Using premium gas in a car designed for regular accomplishes little except a more rapid combustion of your hard earned dollars. Regardless of fluctuating gas prices, we're all conscious of making our fuel spending go further. By familiarizing yourselves with your car's requirements, you will be able to make the right decision when you next stop at your local gas station. Ethanol Producer Magazine – The Latest News and Data About Ethanol Production Octane: What's in Your Fuel?

Minimum octane rating decisions could greatly impact ethanol’s future market opportunities By Kris Bevill | June 12, 2012 At a time when ethanol’s high-octane rating is touted as its most valuable asset, a situation in South Dakota shows a lower-octane gasoline scenario could also emerge. In March, officials at South Dakota’s Office of Weights and Measures began receiving calls from members of the state’s petroleum industry, warning that cheaper 85 octane gasoline had been making its way from the higher elevations in the western part of the state, where it has been historically sold, and into areas where the minimum octane rating is 87. South Dakota, like other states, requires octane labeling, and there was concern that the subgrade 85 octane was being marketed as 87 octane to unsuspecting customers. David Pfahler, director of the weights and measures office, dispatched inspectors who quickly confirmed that some of the stations suspected of selling 85 octane were not labeling the fuel as such.

Word of the inquiry spread quickly among the fuel suppliers, however, and within the first few hours of the inspection blitz, Pfahler says officials began encountering hastily applied 85 octane labels on pumps at stations where the fuel was being dispensed, a last-minute attempt to ward off potential fines. As a result, the state identified just 29 stations of mislabeling 85 octane fuel as 87 or even 89 octane. By mid-May, the situation remained under investigation and inspectors were continuing to conduct fuel label compliance checks, but charges had not yet been filed against any retailer or supplier. Fines for mislabeling fuel, however, are relatively small, punishable by up to 30 days in jail, a $500 fine, or both. Why 85 Octane? The use of 85 octane gasoline dates back to carbureted vehicles manufactured before 1984. Engine knock was known to occur in that type of engine due to a number of factors, with altitude being one of the most significant.

The American Society for Testing and Materials identified regions, primarily in the Rocky Mountains, where lower octane gasoline performed as well in those engines as 87 octane at sea level, and to this day, 85 octane is sold in those regions, despite the fact that vehicles now use computer-controlled systems unaffected by high altitudes. Western South Dakota receives its gasoline from suppliers in neighboring mountain states, so 85 octane has served as the region’s regular unleaded gasoline for decades. The legality of the octane level was never made an issue, but the state’s regulations actually prohibit the sale of 85 octane fuel throughout the state. Suppliers were notified of the regulatory discrepancy after 85 octane use was discovered in eastern South Dakota this spring, but rather than comply, they told the state that 85 octane is the only gasoline provided by area suppliers, so if 87 octane is required, the western region of the state would face gas shortages. Caught in a difficult situation, the state agreed to allow 85 octane gasoline to continue being sold, if properly labeled. Then, in a surprising move, the state said it would propose to legalize 85 octane throughout the entire state.

As of May 17, an official rulemaking had not yet been proposed, but it was anticipated that the state would soon issue an emergency rule to legalize 85 octane temporarily statewide before moving forward with the traditional rulemaking process. Lower Octane’s Impact on Ethanol While perhaps not immediately recognizable, the South Dakota situation bears significant potential consequences for the ethanol industry. No vehicles are currently approved for use with fuel containing an octane level below 87, and because the 85 octane fuel being used in South Dakota is being blended with ethanol, there is concern that ethanol will take the blame for vehicle damage actually caused by lower octane gasoline. “We think people will have problems with it and when they do we’re reasonably certain, from what we’ve seen elsewhere in the country, that it’ll be blamed on ethanol,” says Ron Lamberty, senior vice president at the American Coalition for Ethanol, the Sioux Falls, S.D.-based ethanol industry group. Additionally, because lower octane gasoline can be produced more cheaply, if 85 octane is officially allowed into the eastern part of South Dakota, refiners in neighboring Minnesota may feel pressured to lower octane ratings, beginning a domino effect of refiners reducing octane rating.

“Eventually you create a system where refiners have decided to do something that makes them more money and forced the government to accept it,” Lamberty says. “That can’t happen. That’s why there are standards in the first place.” Perhaps most important in the long run is the potential for octane itself to decrease in value. Ethanol’s 113 octane rating makes it a desirable octane booster in gasoline-ethanol blends, but if low-octane fuels begin to become acceptable in the marketplace, despite automaker warnings and environmental concerns, ethanol’s high-octane rating won’t carry as much value. To be fair, refiners would probably continue blending ethanol to bring the lower octane base fuels up to whatever the newest minimum is, but a regulatory decision to lessen octane’s importance would be a blow to future market possibilities for high-octane fuels. Ford On Board Increasing fuel economy standards for vehicles will require auto manufacturers to design smaller, more efficient engines that continue to satisfy the consumer’s desire for power. Some automakers have already begun introducing these types of engines into the market, the most well-known being General Motors Co.’s Ecotec engine and Ford Motor Co.’s Ecoboost engine.

High-octane fuels have been shown to be the most effective fuel for these types of engines, and some experts have suggested that higher octane gasoline could be beneficial in existing engines as well. Ford researchers noted in a March article in the scientific journal Fuel, that while more research is needed to quantify and optimize the costs and benefits, “substantial societal benefits” may be realized by capitalizing on ethanol’s high-octane rating. In the paper, titled “High octane number ethanol-gasoline blends: Quantifying the potential benefits in the United States,” the Ford researchers, led by Jim Anderson, examine the critical role octane rating plays in the design, operation, efficiency and emissions of spark-ignited engines. The researchers state that higher minimum octane ratings would enable higher compression ratios in future vehicles, improving efficiency, and benefit all spark-ignited engines and hybrid vehicles. “Incorporating ethanol with its inherent high-octane rating is one opportunity to enable an increase in the minimum octane rating for regular-grade fuel,” they said. Anderson and his colleagues point out that despite increasing blending of ethanol into the nation’s gasoline, the octane ratings of regular gasoline have remained unchanged for 40 years.

The researchers attribute this lack of octane increase to petroleum companies modifying their base fuels to take full advantage of ethanol’s octane at a 10 percent blend. In the paper, Anderson’s group says that even if ethanol content is increased, the oil industry can be expected to continue to reduce the octane ratings of its blend stocks so that the final product meets minimum octane requirements, unless government policies raise the minimum octane rating. And, because automakers design the vast majority of their vehicles to operate on the minimum octane rating, the opportunity to increase vehicle efficiencies through the use of higher octane gasoline is limited. “If vehicle manufacturers knew with certainty that the minimum octane rating of fuel would increase at a known future date and remain at these levels, it would be possible to provide future engines that are designed with higher [compression ratios] and operate with correspondingly higher thermal efficiencies, which could also provide the potential for engine downsizing and turbocharging to further improve fuel economy,” the researchers said. Interestingly, the researchers note that the “logical first step” towards improving the nation’s octane rating would be to eliminate the use of 85 octane fuel in high altitude regions and establish a nationwide minimum octane rating.

“This relatively simple change would affect a very small fraction of fuel produced, but would have an immediate efficiency benefit for vehicles using such fuel in those areas of the country, and would allow more efficient future use of nearly all fuel used by the [light-duty vehicle] fleet in the U.S.,” the researchers wrote. Anderson and other Ford researchers also contributed to a paper recently published by global automotive engineering association SAE International that details research funded by ICM Inc. and conducted by AVL Powertrain Engineering Inc. to examine several aspects of increased ethanol blends as related to vehicle fuel systems. The paper, titled “Effect of Heat of Vaporization, Chemical Octane, and Sensitivity on Knock Limit for Ethanol-Gasoline Blends,” was co-authored by experts at AVL, Ford, BP Products North America Inc., Deere & Co., and Steve Vander Griend, head of research and development of ethanol engines at ICM. AVL researchers tested a number of ethanol blends during the study, ranging from E0 to E98, and found that when ethanol content is increased, the knock-limited performance and the thermal efficiency of engines significantly increases, particularly in turbocharged direct-injection engines.

Vander Griend says the most exciting part of the study is that it demonstrates ethanol’s full value as a fuel. “There is value beyond E10 by simply adding ethanol,” he says. “When you give more octane via ethanol, you increase the range of efficiency.” Auto manufacturers still need to determine what their ideal octane rating will be before the ethanol industry can begin targeting a specific blending ratio, but based on current and previous research data, Vander Griend says he believes E30 could be “a great starting point” because it offers the increased cooling effect desired for fuel efficient engines and a research octane number, or RON, of about 100. The Ford researchers stop short of identifying an optimal ethanol blend in their paper, but note that large increases in octane could be possible by blending 10 to 20 percent more ethanol into the 10 percent ethanol blends currently on the market. Not surprisingly, the petroleum industry has yet to express a willingness to increase the U.S. minimum octane level. “We feel the three levels of octane currently available serve the customer best,” says Bob Greco, downstream director for the American Petroleum Institute.

He admits that refiners have adjusted their blend stocks to produce gasoline that meets minimum octane requirements when blended with ethanol. Ethanol’s high-octane rating is its most desirable property to blenders, he says, but he declined to discuss the financial benefits for refiners who take full advantage of ethanol’s high-octane by using lower-cost blend stocks, stating that the costs vary on a refinery-by-refinery basis. According to Greco, consumers have the option of purchasing higher-octane fuels so there is no need to increase the minimum. But Anderson and his fellow researchers pointed out in their paper that as long as fuel with a high ethanol content and/or high octane number is classified as a premium grade gasoline, manufacturers will not optimize their vehicles to use the niche fuel. “Ideally, for a maximum societal benefit and to ensure a successful transition, the minimum octane ratings of all U.S. gasoline should be increased, rather than positioning the high ethanol content/high octane number fuel as a premium grade,” the researchers say in the paper. ACE’s Lamberty also believes the future of the ethanol industry will focus greatly on its octane rating and the benefits of high-octane fuel.

Ethanol is currently the cheapest, cleanest, highest-octane fuel available, and Lamberty says producers who were focused primarily on expanding and improving production just a few years ago will be paying more attention to increasing the value of their fuel now that the industry has matured. And if value is the focus, octane will be the subject of interest. “Anything we can do to maximize ethanol’s position as an octane product rather than just as an extending product is where we’ve got to move that product eventually,” he says. “Overall, the volume of gasoline or gasoline replacements being sold is not going to go up, so other than just making gallons, the next thing we have to establish as an industry is our value as octane.” Author: Kris Bevill

Question: Regular American gasoline has what octane rating?
Answer: 87