Fuel-Saving Driving Myths That Persist Despite the Evidence

This advice made sense for carbureted engines common before the 1980s, which needed time to stabilize fuel mixture at low temperatures. Today's engines use electronic fuel injection and sensors that adjust in real time. Extended idling burns fuel without moving the vehicle, increases engine wear by running in a partially warmed state longer than necessary, and contributes to emissions. In most conditions, 30 seconds of idling is sufficient before driving away — just keep acceleration moderate for the first few miles.

Aerodynamic drafting does reduce drag in controlled motorsport environments, but the following distances required to achieve meaningful effect — often less than 100 feet at highway speeds — eliminate virtually all stopping distance. At 65 mph, a passenger car travels roughly 95 feet per second. A sudden truck brake event at that gap is not survivable in most scenarios. The U.S. Department of Transportation and safety researchers consistently categorize tailgating large vehicles as a high-risk behavior. The marginal fuel benefit does not offset the risk. For more on what actually creates aerodynamic drag on your vehicle, see why your engine works harder on the highway.

The octane rating of gasoline indicates its resistance to premature ignition (known as engine knock), not its energy density. Engines requiring premium fuel are designed with higher compression ratios or turbocharging that would cause knock on regular. If your owner's manual says regular fuel is recommended (not required), adding premium is simply spending more money per gallon with no return. The EPA and independent automotive testing have consistently found no fuel economy difference in regular-spec engines running premium.

This one has a grain of truth at low speeds. In stop-and-go city traffic, running the AC does add measurable load to the engine, and open windows have little drag impact. But around 45–55 mph and above, the aerodynamic penalty of open windows grows substantially. Research from SAE International has found that at higher speeds, the fuel cost of the drag from open windows can match or surpass the cost of the air conditioning compressor. The practical takeaway: use windows in city traffic, use AC on the highway, and use your vehicle's recirculate setting to reduce compressor cycling.

When a fuel-injected engine is in gear and decelerating — foot off the throttle — the engine management system cuts fuel delivery almost entirely because the wheels are driving the engine rather than the other way around. In neutral, the engine still burns fuel to maintain idle speed. Coasting in neutral also removes engine braking, which can increase wear on friction brakes and reduces the driver's control over vehicle speed. Most driving instructors and automotive engineers recommend staying in gear when decelerating unless coming to a complete stop.

There is a kernel of physics here — a harder tire does have slightly less deformation contact with the road — but the trade-offs are significant. Over-inflated tires have a smaller contact patch, which reduces grip in wet and emergency conditions. They also wear unevenly in the center and are more susceptible to damage from road impacts. The manufacturer's recommended pressure, printed on the door jamb sticker, is the result of engineering balance between efficiency, safety, and durability. Staying within that range — and checking it monthly, since tires lose roughly 1 PSI per month naturally — is the evidence-supported approach.