I was thinking as of late ethanol is used as the primary additive to raise the octane rating of pump gas.
Many of not most states mandate 10% ethanol in pump gas.
If the octane number on the pump for a given grade is a minimum number rather than an absolute number is it possible the lower labeled grades actually have the same or higher octane rating than the premium fuels labeled at 92 or 93?

I found Georgia's regulations that state the following:
"The motor octane number must not be less than 82 for unleaded gasoline with a minimum (R+M)/2 octane rating 87"
This suggests that the number on the pump is a minimum supporting the theory that we may be purchasing premium-priced fuel for no reason.

Other's thoughts?
Andy

 

I think it would be highly unlikely that the major or independent gas stations would be giving away anything these days, much less higher octane than the pump indicates. We're probably lucky if we get what's posted.

 

The ethanol mandate was initially put into effect back in 2005. It's my understanding that when the two fuels are blended the net result is the Min stated number on the pump but not much more.