You’d think, then, that premium gasoline would be better for your car, especially given the price hike of the highest grade compared to the cheapest stuff. After all, there has to be some advantage to the more expensive fuel, right?
Not so fast. Those numbers associated with each grade of fuel refer to the octane rating of that particular gasoline. An octane rating is a standard measure of performance for the gasoline we buy every day. The higher the octane number, the more compression the fuel can withstand before igniting in an engine’s cylinder chamber.
In broad terms, gasoline with a bigger octane rating is used in high-performance engines that deploy higher compression ratios to make their gonzo levels of power. The pistons in those engines are squeezing their air/fuel mixture in the cylinder chamber so forcefully that it needs all the help it can get to run properly. A high octane fuel provides that help by furnishing a bigger bang during each piston stroke. Audi recommends using a high octane fuel for its high-strung Audi RS3, for example.
Due to its marketed name, consumers may confuse “premium” gasoline for “better” gasoline. This is not surprising and completely understandable given the dearth of information provided by fuel companies on their products to the average consumer. This is where a lot of common misconceptions arise.
Because the majority of engines are designed to run just fine on 87-octane fuel, putting the expensive stuff in a lower-compression engine will have no effect other than needlessly hoovering money out of your wallet. It won’t make your car run any better or worse, so if you decide to fuel up your car with premium gasoline as a sort of treat, you’re simply giving it a placebo. It won’t run any better, your fuel economy won’t increase and the car won’t be any better off for the experience.