Recently, I discovered something that others have known for a while but many don’t know. Namely that effectively all modern cars that say they should use Premium (high-octane) gasoline run perfectly fine on regular. Since the early 90s, cars have had more advanced carb/fuel-injector systems which adjust to the octane of the gas and don’t knock. Like an idiot, I’ve been filling my car with premium. The engineers at all the major car vendors have confirmed this.

I worked out that since the USA uses 370 million gallons of gas a day, or 135 billion per year, at 12% premium sales, that’s 16 billion gallons of premium sold, almost none of it needed. Call it 15B gallons. At a surcharge of 20 to 30 cents/gallon that’s over 3 billion extra dollars charged to no purpose in the USA, and presumably another 3 billion outside (though perhaps they buy less hi-test outside.) The USA uses about 44% of world gasoline.

So why do many cars come with a line in the owner’s manual saying to use premium gasoline? Turns out the marketing departments believe customers of higher-end cars are ethralled by horsepower. They want to advertise the highest peak horsepower number they can. And you can deliver a slightly higher peak horsepower on higher octane. Nothing so big that you would notice it outside of extreme driving conditions or pro racing, but you can publish a higher number. So long as you spec the car as using premium.

So to satisfy these marketing numbers, the world is spending about 6 billion extra bucks each year on high octane fuel. And I’m not even considering all the extra infrastructure required (fancier pumps and blending systems, more tanks with risk to leak into the ground etc.)

Many people think high-octane gasoline is “more powerful.” In fact, oddly, the octane rating measures how non-explosive the fuel is. The higher the octane, the less likely it will explode under pressure. People think of high-octane fuel as more powerful because with high octane fuel, you can design a higher performance car that works at higher compression, safe in the knowledge you won’t get explosions from anything but the spark plug, ie. knocking. The fuel is not higher power, it’s the engine, which is why putting premium into a regular car is a waste unless it’s knocking. Lead cheaply reduces knocking at low pressure which is why they used to add it until they realized, “holy crap, we’re filling our fuel with toxic lead!”

There is still controversy over whether high-compression engines get better mileage than when they run at lower compression with regular.

What a scam. Spread the word.