Mandotim, years ago, the story I heard was that when they broke down crude, there was a proportion that could be turned into petrol/gasoline, some that could be lubricating oil, and some that could be diesel. They couldn't turn the crude oil into any one of anything, so they needed to sell a balance of the fuels.

I don't know if advances have changed that. The story is 30 years old. If it is still the same, we can't ALL use diesels.

Diesels will burn lots of different oils, of course, but all the others are more expensive to produce, or need special conditions of storage, or grow bugs, or are more polluting, or suchlike problems.

When we last visited the UK, we did about 1000mls in a borrowed diesel Peugeot. Impressive and frugal.