You’ve probably heard the old trick: Pull up to a gas pump right after a fancy luxury car leaves, and you’ll get a little bit of the premium gas they left in the pump’s hose added to the 87-octane swill you’re buying. Suddenly, magically, you’ve got a little extra octane in your tank for free. Well, hate to burst your bubble, but that’s simply not how it works.
Ari Henning over at RevZilla did the math, and found that even the longest hoses you’ll find at your average gas station can only hold a few measly cups of gasoline. Even in small motorcycle tanks that’s rarely enough to make a difference, and it certainly won’t move the octane needle in your car.
According to Henning’s numbers, the longest common gas hose can hold 30 ounces of fuel. That’s just 1.2 percent of the capacity of a Miata’s fuel tank, meaning your carefully acquired high-octane fuel will be entirely lost in the mix of whatever you’re actually paying for — particularly if you drive any car with a tank bigger than the Miata’s, which you probably do.
The “sneak some high-octane fuel leftover from the last driver” trick sounds fun, but it’s not really going to get you any benefit that your car will notice. If you’re going to keep following those Bentleys or tuned STIs into the local Sheetz, just know you’re not getting anything out of it — it’s all for the thrill of the hunt.