Top 5 MYTHS OF FUEL EFFICIENCY DEBUNKED.

But before you can start saving, you need to separate fact from fiction. Here are the top 5 myths of fuel efficiency—debunked.

Myth #1: Using Cruise Control Always Saves Gas

The Truth: Cruise control can help you burn less fuel—but only under the right conditions .

Maintaining a steady speed means less acceleration, which burns less fuel. But the speed you select is critical. Setting your cruise control at 55 mph is great for efficiency. Anything over that, and you'll reduce your miles per gallon as aerodynamic drag increases .

The Bold Truth: According to Consumer Reports tests, increasing speed from 55 mph to 65 mph cut fuel economy by 8 mpg in a RAV4 and 6 mpg in an Altima . And on hilly terrain? Cruise control can actually hurt your MPG as the car aggressively compensates for inclines .

Myth #2: Manual Transmissions Are Always More Efficient

The Truth: Thirty years ago, this was true. Manuals were typically 5% more efficient than automatics .

The Bold Truth: By the 2010s, automatic transmissions had caught up—and surpassed—manuals. Modern automatics now have 8 or 10 forward gears (compared to 5 or 6 in manuals), making them actually more efficient . Today, choosing a manual doesn't guarantee better fuel economy.

Myth #3: Turning Off Your Air Conditioning Saves Gas

The Truth: Yes, using your A/C cuts into gas mileage. But open windows create enough wind drag to offset those gains .

The Bold Truth: If you open your windows above 40 mph, you're losing more efficiency than if you just run your A/C . The sweet spot? Below 40 mph, roll the windows down. Above 55 mph, use the A/C . At highway speeds, the aerodynamic penalty from open windows outweighs the fuel used by the compressor.

Myth #4: Turning Off the Engine or Shifting to Neutral Saves Gas

The Truth: Idling is the enemy of efficiency—your engine burns gas without moving the car. But putting the car in neutral has no impact on efficiency because the engine is still running .

The Bold Truth: For modern engines, idling for more than 10 seconds uses more fuel than simply turning the engine off and restarting it . Many modern cars feature auto stop/start that does exactly this—and it's a definite gas saver, especially at stoplights or in bad traffic .

Bonus: There's no need to "warm up" your modern fuel-injected car before driving. Just start it and go—unless it's extremely cold out .

Myth #5: Keeping Your Tank Full Improves Fuel Economy

The Truth: Having more gas in your tank adds extra weight, which can actually take more gas to move .

The Bold Truth: For optimal efficiency, experts recommend keeping your tank half to a quarter full—assuming you don't mind the extra fuel stops . But don't go too low! Regularly driving with the needle near empty is hard on your fuel pump and can cost you hundreds of dollars in repairs down the road .

What Actually Improves Fuel Economy

Now that the myths are busted, here's what actually works :

Slow down and steady up: The sweet spot for fuel efficiency is 35–55 mph. Keeping your speed steady, accelerating smoothly, and leaving plenty of room in front of you minimizes fuel consumption.
Lighten your load: Every extra 100 pounds reduces fuel economy by about 1-2%. Clean out your trunk and remove roof racks when not in use. Consumer Reports tests showed that carrying bikes on a rooftop cut fuel efficiency by 19% to 28% .
Maintain your vehicle: Proper tire pressure, good wheel alignment, and regular oil changes help your car operate as designed. Under-inflated tires increase rolling resistance and hurt your MPG .
Skip the premium gas: If your vehicle doesn't recommend or require premium fuel, using it offers zero benefit .

The Bottom Line

Fuel costs are one of the biggest household expenses in Illinois—and with prices hovering above $4.50 per gallon, every mile counts. Whether you're driving through Joliet, commuting from Plainfield, or running errands in Bolingbrook and Crest Hill, understanding these fuel efficiency myths can save you real money.

Here at Gerald Auto Sales, we've been helping drivers in the Joliet area for over 30 years find reliable, fuel-efficient vehicles. With over 30 cars in stock that get 30+ MPG and a 4.7-star customer satisfaction rating, we're committed to making sure you drive away with a vehicle that fits your budget—both at the dealership and at the pump .

Stop by our lot at 314 South Larkin Avenue in Joliet, or give us a call today. Let's find you a car that goes further on every gallon.