nglitz,

Here's a bit of info I discovered, that confirms that detergent additive concentrations vary by gasoline grade.

I've seen no mention of a law against it, nor can I fathom a reason as to why there would be one.

http://www.chevron.com/prodserv/fuels/techron/techback.shtml

Also, detergents, though they are additives, are not necessarily octane boosters. Their purpose is to reduce deposits in all fuel system components, as well as in the combustion chamber.

I've had more than a few modern engines apart, and only those very poorly cared for have any serious "white" or "yellow" deposits in the combustion chambers. I have seen this phenomena in those low mileage Japanese engines that receive ZERO maintenance. Deposits are also determined by your driving style. If you baby your engine all the time, deposits will form more quickly.

From all evidence I can find, octane is still determined by the fuel and additives that increase the length and or strength of hydrocarbon chains.

Modern fuel injected engines do not run constantly lean or rich unless they are not in normal operating condition.

Oil burning may seem like a deposit former, but again, excessive oil burning is a state of disrepair. If your engine burns enough oil to quickly form deposits, it needs to come apart.

Justin