“The worst thing about myths is that they’re usually untrue.” Sounds like a stereotypical Yogi Berra-ism, right? (Nope. That one’s ours.) Well, over the years, some absolute whoppers have developed over what does and doesn’t affect gas mileage.
While certain factors—driving style certainly a top contender—have been proven to greatly impact mpg, a lot of grade A baloney has been sold to consumers over the years.

Over the years, some absolute whoppers have developed over what does and doesn’t affect gas mileage.
Proponents of these ideas might be well-intentioned—after all, gas prices are nothing to scoff at—but they’re not well-informed. To clear up some misconceptions, we’ve compiled a list of gas-mileage untruisms. The following ideas are all, pardon the expression, “outta gas.”
Myth #1: Dirty air filters slurp gas.
Reality check: OK, this one has some merit…in the past. Older engines did suffer at the hands of a dirty air filter, but computer-equipped modern engines govern the air/fuel ratio so effectively that the air filter no longer is a huge part of the equation. Caveat: A dirty air filter might negatively impact acceleration.
Myth #2: Open windows waste fuel.
Reality check: Here’s the theory: Rolling down the windows to get a face full of wind at 55 mph and above negatively impacts a car’s aerodynamics. The problem is that tests have failed to indicate this affects gas mileage. Theory debunked.
Myth #3: It’s important to warm up the engine.
Reality check: Again, this has an element of truth…if you’re driving a vintage DeSoto. If you’re operating a modern vehicle—no way. Today’s fuel-injected, computer-run engines are a heckuva lot snappier at the get-go. Sitting in your vehicle, idling the engine every morning is only wasting gas. For a detailed explanation, click here.
Myth #4: Premium gasoline provides improved fuel economy.
Reality check: Visit a gas station and you’ll typically see three grades of gas listed on the pump: regular, midgrade and premium, with octane ratings typically 87, 89 and 93, respectively. Certain vehicles—hot-running sports cars and luxury vehicles—require premium, which helps prevent “pre-ignition,” a situation where the air/fuel mixture in an engine cylinder ignites before a spark plug fires. High-octane fuels also help ensure high-performance engines realize their full power. However, the bulk of the vehicles on the road don’t run nearly as hot and aren’t susceptible to pre-ignition. They’ll do fine with regular-grade gas and won’t perform better or achieve better mpg using premium gas. Get into the nitty-gritty on this subject by clicking here.
Myth #5: If it ain’t got a red Pegasus or yellow seashell, it’s trash gas.
Reality check: Companies such as Mobil, Shell and BP don’t have a monopoly on good gas (even though they might like to.) Here’s the real deal: Independent filling stations purchase their gas from name-brand oil companies, so their fuel doesn’t differ from the more expensive big-corporation version. Seashell and Pegasus gas might contain engine-cleaning additives, however, but experts say their absence shouldn’t impact most cars.
Myth #6: Low-rolling-resistance tires are the way to go.
Reality check: Not so fast, there. Tire rolling resistance is the amount of energy required to roll. Lower resistance=higher fuel economy. But this simple—even simplistic—view ignores the bigger picture of what we rely on tires to do: aid in stopping, provide safe handling and avoid hydroplaning. Experts warn that certain tire models achieve their low rolling resistance by sacrificing wet-weather performance and decent tread life. It’s best to relegate rolling resistance to a minor consideration when purchasing tires. Instead, buy a safety-focused set and keep them properly inflated to maintain safety and realize maximum mpg.
Had enough of this nonsense? To find ways to truly maximize your mpg, read “Guard against the guzzle: Gas-saving guidelines” and “Lead foot? Pack rat? 13 ways to save gas by changing your driving habits.”
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