The 91 does not say "Contains 10% Ethanol" either. Costcos in CA have a 20c to 30c spread between 87 & 91 so about 5%.
Originally Posted by Wolf359
Wow, that's a really big spread between regular and premium. The mid grade is a real money maker though, should be half of regular and half of premium so it should be $3.25 instead of $3.70. So they make an extra 45 cents per gallon.