Sitka is correct. I'm an old gasoline blender that made zillions of gallons of gasoline, of which 99.8% or more was on-spec. Gasoline isn't a liquid stream that comes from crude as such. It's a blend of several gasoline blending materials that are combined in varying proportions to produce a gasoline that is acceptable for use in the regions of the country. Gasoline for Denver isn't the same as gasoline for Florida, and then there are summer grades and winter grades. And then, and always, Uncle Sam is watching and testing to make sure we aren't making off-spec gas and cheating the public. Big trouble if you knowingly market bad gas.
Refining crude to make gasoline, LPG, heating oil, diesel, 2 Oil, 6 Fuel, various chemicals, and this and that is a very interesting process. Pretty much every drop of crude oil winds up being used. The term "toxic Byproducts" really doesn't apply, though I suppose you could call all types of petroleum products toxic, in that if you swallowed them they would do you harm and might kill you - depending on how much you ingested.
But, back years ago, prior to a lot of materials (benzene for instance) being found to be carcinogenic, we didn't worry about getting it on us or breathing the fumes. And oddly enough, as we aged I lost several former friends and coworkers to cancers and other things.
