Why do we use gasoline and not crude oil in our cars?

See here Oh wait, this is actually about using crude oil for lubricant, not as fuel.

Your question is so far off base, that it’s hard to find anyone answering it.

It looks like if you put even a little bit of motor oil in a tank with gasoline, you get lots of blue smoke and problems.

If you put only oil (not to mention crude oil), it just won’t run. Gasoline engines work by exploding some gasoline vapor, which works because it is clean and works that way, which crude oil doesn’t.

Gasoline atomizes better and it’s flash point is more conducive to proper ignition. And gasoline was a waste product before cars were invented, when kerosene was needed for lamp oil. Heavy oil sets up like peanut butter in cold conditions, which makes it not useful for compression ignition engines, like Diesels, which use an anti-gel ingredient to keep the fuel flowing when it’s cold.
Diesel engines came along in the mid 1910’s when Diesel was trying to make a compression engine that ran on coal dust. (The first such engine exploded.) It was thought that German agents had him killed during WWI.
Also, a compression ignition engine needs very high compression to ignite the fuel, like about 22:1. And a Diesel engine will run on motor oil. Or gear oil, or vegetable oil, or automatic transmission oil,... Just about any kind as long as it flows and isn’t like peanut butter or regular grease lubricant.

The same reason we drink glasses of water and not glasses of mud…

Basically, engines were made to run on gas, not crude.

You can’t even use diesel fuel in a gasoline car. Even a very small amount of diesel fuel that is accidentally pumped into a gas tank can clog up the engine.

Well, actually, the gas engine will blow blue smoke from the Diesel fuel that doesn’t burn well. Too much and the gas engine won’t run at all.