I agree that the additives are assinine, but I don't think the gasoline burns as cleanly without them. If the oil companies didn't have to buy ADM ethanol to put in their product to make it meet CARB standards, they wouldn't.
It depends upon the car. The mix standards were designed for cars built ten years ago. Cars built now would run cleaner on gasoline without oxygenate than cars built ten years ago operating with oxygenate, even when new. OTOH, cars built thirty years ago are MORE polluting than they were before the introduction of MTBE. The reason is that they produce more evaporative emissions than without the oxygenate because the stuff is far more volatile. I have never seen an analysis of that fact (studies of Mexican owned cars and pollution are NOT PC), but I would bet that with the evaporative component that there was no net benefit to adding MTBE at all, never mind all the other environmental problems that came with it.
If the oil companies didn't have to buy ADM ethanol to put in their product to make it meet CARB standards, they wouldn't.
That's not how it worked in California for the first CARB RFG mix. They actually specified the content of oxygenate required in the mixture and demanded more MTBE than was optimal. Moreover, there were only two air basins that needed oxygenates by EPA standards. CARB mandated it for the whole state (as they are doing again). Pete Wilson's wife was then put on the BOD at ARCO. I have little doubt that there is a political payoff involved in setting the new mix specifications.