Gas Mileage Myths That Need Busting

Because your uncle’s “tap the gas twice before turning the key” routine isn’t science

Fuel economy is one of those topics everyone thinks they know about. It’s like the car world’s version of nutrition—plenty of opinions, a few half-truths, and a lot of outdated advice passed down like family folklore. And while gas prices bounce around like a toddler on a sugar high, drivers are more eager than ever to squeeze every mile they can out of a tank. But before you start coasting down every hill or turning off the A/C in 90-degree heat, let’s bust a few persistent myths that are probably doing more harm than good.

Myth #1: Warming up your car improves fuel efficiency

This one’s been around since the carburetor days, but modern engines don’t need five minutes of idling before they’re “ready.” In fact, idling gets you precisely zero miles per gallon. Today’s fuel-injected engines are designed to start and drive almost immediately. So unless you’re in sub-zero conditions and just trying to get the heater going for comfort, you’re not doing your MPG (or the environment) any favors by letting your car run in the driveway while you finish your coffee.

Myth #2: Premium gas = better mileage

Unless your car specifically requires premium fuel, filling up with high-octane gas is just expensive optimism. Premium gas isn’t magically more efficient—it’s just formulated to withstand higher compression in performance engines. If your owner's manual says regular unleaded is fine, premium won’t give you extra mileage or power. It’s like feeding a house cat filet mignon and expecting it to start catching bigger mice. Not gonna happen.

Myth #3: Manual transmissions are always more fuel efficient

Once upon a time, manuals ruled the MPG game. But modern automatic transmissions, especially those with continuously variable transmissions (CVTs) or 8- to 10-speed setups, are now just as efficient—sometimes more so—than stick shifts. Technology caught up, and unless you're driving a bare-bones economy car or just really love clutch pedals, the savings probably aren’t what they used to be.

Myth #4: Turning off the A/C saves tons of gas

Okay, this one’s… sort of true. Running your air conditioning does use extra fuel, but it’s not the gas-guzzling villain it's made out to be. On hot days, rolling down the windows instead can actually make your car less aerodynamic—especially at higher speeds—meaning your engine has to work harder to push through the wind. The real-world difference is often small, and comfort matters too. If you're stuck in traffic in August, just turn on the A/C and enjoy the ride guilt-free.

Myth #5: More fuel-efficient cars are always cheaper to run

Not necessarily. Fuel economy is only one piece of the total cost puzzle. Hybrid and high-efficiency cars can be more expensive to buy and maintain, and if you’re not driving enough to see long-term fuel savings, the math might not work in your favor. That’s not to say they aren’t great options—just don’t assume that 50 MPG automatically means cheaper ownership than your cousin’s trusty Corolla.

Myth #6: Keeping your tank full improves mileage

Nope. The only thing a full tank helps with is peace of mind. In fact, more fuel means more weight, and more weight can slightly reduce your efficiency—though the difference is almost too small to measure. Still, if you’re hoarding gas thinking it boosts MPG, it’s time to let that myth go.

What does help?

Good habits. Keep your tires properly inflated. Lay off aggressive starts and hard stops. Travel light. Combine errands. Use cruise control on the highway when possible. And don’t forget regular maintenance—a clogged air filter or misfiring spark plug can tank your fuel economy more than any bad myth ever could.

Gas mileage isn’t magic, and it definitely isn’t improved by folk tales and wishful thinking. Once you let go of the myths, you can focus on the stuff that actually works—and maybe even enjoy the drive a little more in the process.

So next time someone offers you fuel-saving wisdom that sounds like a TikTok trend gone rogue, just smile, nod, and remember: science > superstition. Every time.