> I'm so sorry that 42% isn't quite most

It is nowhere near 42% if you're thinking just crude instead of all petroleum products, which our discussion is about refining crude oil. According to numbers from the EIA which I provided above. 13 - 4 == ???

> As far as your thinking that it's not difficult to change a refinery over, do some research.

I have a pretty long history of knowing about oil refining. Reading patents about cracking heavy crude was literally childhood reading material for me, as a son of an IP lawyer for Exxon working out of the Baytown plant in South Houston. Let me share with you how refining works at a high level, and then you'll hopefully better understand. It is probably literally in my blood, as I grew up less than 10 miles from some of the densest area of refineries on the planet and groundwater contamination is a thing. Over half of my family friends growing up worked at the refineries, the others mostly worked at NASA. Many of my close friends work in the O&G industry.

Start off with the basics. Light, sweet crude. This stuff is trivial to process, we've been doing it for over a hundred years. All you need is a regular distillation tower setup and condensers. Heat it up at the bottom, manage the pressure in the column, and it all separates out into different grades. It is pretty much all shorter chain petroleum products (light), it flows easily, and doesn't have a lot of contaminates (sweet).

Ok, so let's move on to light, but sour. This means the oil has some chemical contaminates, usually sulfur is the big one. So we need to first take this light and sour oil and send it to systems that react with the sulfur compounds but don't react with the rest of the oil to foul it all up. Now we have light and sweet oil, which hey we just mentioned we already know and have equipment to process. Its then the exact same stuff that we had before.

What about heavy? Heavy means it has a lot more long-chain petroleum products in it. Stuff like tar and what not. So now we need to heat this up and have stronger pumps to move it around, so that makes it a lot more complicated even just receiving it. We need to send it to special "crackers", which have lots of fancy catalysts and tightly controlled reaction chambers which break these longer chain petroleum molecules into...lighter, shorter petroleum molecules. What do you know, after we crack it, we're back to having light oil again. And we send that along to the same equipment that we used in the first example.

But what about heavy and sour you ask? Well, that means we need to first crack it, then process the sulfur, and then hey what do you know we're back to working with light and sweet. That thing we already talked about being easy to process.

So what does it mean to take a refinery designed for heavy and sour and change to light and sweet? It means you redo some plumbing to bypass your cracker and sulfur reactors, and just use the regular distillation column you already had. It is massively expensive to go from light and sweet to heavy and sour, but it is pretty trivial to go from heavy and sour to light and sweet. You always have to have the equipment to process light and sweet, but the equipment to handle heavy is kind of rare and very expensive. Literally billions to go one way, and maybe several hundred thousand to go the other way if they didn't leave the valves and plumbing in place to send stuff straight to the columns. The biggest hit to capital is the write down from all the billions of dollars worth of equipment you're no longer using.

The oil industry has already been converting many refineries to process only light and sweet. They're not spending billions in new capex these days what with the uncertain future of oil demand. What does that tell you about the costs?