Keeping Your Vehicle in Shape

The check engine light, or malfunction indicator lamp, on your dash board indicates that something is wrong with your engine. Modern vehicles are so advanced that they may seem to drive normally even when a repair is needed, which sometimes leads drivers to ignore the indicator.

It could be something as minor as a loose gas cap, but it could also be a more serious issue that could reduce your fuel economy, increase emissions, and/or lead to costly repairs later.

So, when the check engine light comes on, have your vehicle inspected by a mechanic. It could save you fuel and money down the road.

You can improve your gas mileage by 0.6% on average—up to 3% in some cases—by keeping your tires inflated to the proper pressure. Under-inflated tires can lower gas mileage by about 0.2% for every 1 psi drop in the average pressure of all tires. Properly inflated tires are safer and last longer.²

The proper tire pressure for your vehicle is usually found on a sticker in the driver's side door jamb or the glove box and in your owner's manual. Do not use the maximum pressure printed on the tire's sidewall.

You can improve your gas mileage by 1%–2% by using the manufacturer's recommended grade of motor oil. For example, using 10W-30 motor oil in an engine designed to use 5W-30 can lower your gas mileage by 1%–2%. Using 5W-30 in an engine designed for 5W-20 can lower your gas mileage by 1%–1.5%. Also, look for motor oil that says "Energy Conserving" on the API performance symbol to be sure it contains friction-reducing additives.¹

Replacing a clogged air filter on vehicles with fuel-injected, computer-controlled gasoline engines—such as those manufactured from the early 1980s to the present—or diesel engines does not improve fuel economy, but it can improve acceleration.

Replacing a clogged air filter on an older vehicle with a carbureted engine can improve both fuel economy and acceleration by a few percent under normal replacement conditions.^{3, 4, 5}