Are all gasolines the same?

Question

For instance , is Shell better than BP,or is 87 octane the same everywhere?

Answer 1

Unless a gas station is (illegally) diluting their gasoline with another substance, 87 octane is the same everywhere in the United States.

In other countries, however, they don't use the (R+M)/2 method for calculating octane, so they will always report a higher octane for the same fuel. For example, gasoline with 87 octane in the US might be measured as 92 octane in Europe or Asia, despite being the exact same thing.

Answer 2

There are only a few places that actually refine petroleum here in the us so the answer is yes they are all almost exactly the same. Though some add more detergent they all have to follow the same laws governing additives and octane levels.