# Automobile Repair/Optimizing Fuel Economy

There are many factors that can affect your vehicles fuel economy, many of which are directly related to routine maintenance that you can perform yourself. While there are many products on the market that claim to boost the fuel economy of vehicles few if any of them deliver on their claims. The best ways to get good fuel economy include careful driving and keeping your car properly maintained.

## Tire Pressure

One of the simplest ways to maintain good fuel economy is to ensure that your tires are properly inflated. The owners manual for you vehicle will indicate the proper pressure to inflate you tires to. There is often a sticker or other label along the driver’s side door of vehicles that also states the manufacturer recommended pressure. Decreased tire pressure increases the rolling resistance of your tires and decreases fuel economy, and may also increase tire wear and impair performance.
There are some who believe that over inflating tires will further decrease rolling resistance and increase fuel economy, however over inflated tires often suffer from excessive wear, and impaired grip. Tires that are extremely over inflated can lose enough grip to cause safety problems in the event of an emergency stop, so it is strongly recommended that you never exceed the maximum pressure rated on the sidewall of your tire.

## O2 Sensor & Thermostat

Both the thermostat and on modern cars the oxygen or O2 sensor can affect fuel economy and should be replaced either at a manufacturer recommended interval or when a electronic fault code/ low temperature problem is detected. Electronically fuel injected vehicles have an O2 sensor or sensors in their exhaust system which helps the vehicles computer determine how to optimize fuel economy. These O2 sensors may need to be changed periodically for a vehicle to optimize it's air fuel mixture and maximize it's fuel economy. Thermostats optimize the flow of coolant and help a vehicle maintain it's proper operating temperature, which is important in fuel economy. If a vehicle has trouble reaching it's optimum operating temperature the thermostat is usually the main suspect and should be changed.

## Air Filter

It is highly recommended that you check your vehicles air filter periodically and insure that it is clean, especially on older vehicles. Black or otherwise dirty air filters make your engine work harder to get enough air for proper combustion and decrease its efficiency; however, electronically fuel injected cars can automatically compensate for the decreased air flow caused by a dirty air filter and experience relatively little decrease in fuel economy. The main problem caused by dirty air filters in modern electronically fuel injected cars is decreased acceleration/performance. Most owners’ manuals will recommend a service interval which you should change your air filter at, but periodic visual inspection is the best way to ensure that your air filter is clean.

## Proper Oil

Making sure to use the recommended weight of oil can decrease the burden on your vehicles engine and keep your vehicle under warranty. Heavier oil weights such as 20W-50 are harder to push through you engine than say 10W-30 or 5W-20 oils, which can cause a decrease in fuel economy. Overweight oils have traditionally been used in high mileage engines that had small oil leaks and/or heavily worn components (bearings etc.), both of which could be remedied with heavier oil because it wouldn't seep out as easily and it would properly fill worn engine components, but wear is far less of an issue on modern cars. Modern engine manufacturing and lubricants have decreased engine wear to the point that modern engines should never need an overweight oil even with hundreds of thousands of miles/kilometers on an engine. There are some ultra light weight oils available such as 0W-20 which may be labeled as being for hybrid vehicles; however, using too light of an oil could potentially harm your engine and void any warranty on your vehicle so you should consult your vehicles manufacturer before trying an underweight oil. There are some who under fill their oil in order to further lower internal friction and increase fuel economy; however, if any oil is lost due to leaking or burning the engine is in much greater risk of catastrophic failure and may not be covered under warranty.

## Changing Behavior

Although it's not maintenance, altering driving behavior can significantly improve fuel economy. Increase following distance so you don't need to make constant corrections for the vehicles in front of you. Tailgating might lower your wind resistance, but being forced to stop because the car in front of you is turning can easily undo any gains, not to mention the risk of getting a ticket or having a crash. Try to avoid sudden stops and hard acceleration. Slow down before arriving at red traffic lights, so they might turn green before you reach them, and you can possibly avoid stopping at all. Also slow down before joining a line of cars at a stop sign, so you don't need to stop and go multiple times. Similarly, when caught in a traffic jam, it is more efficient to creep forward at a constant speed, than to charge forward and stop with every traffic wave. Avoid excessive speed, as the power required to fight air resistance is proportional to the cube of the velocity (For example, going twice the speed requires 8 times the power). Backing in to a parking space, while the engine is warm, is more efficient than backing out after it has cooled.