How can I improve my car's fuel efficiency through maintenance?

Keep Your Tires Properly Inflated

One of the simplest and most effective ways to maintain good fuel economy is checking your tire pressure regularly. Underinflated tires create more rolling resistance, meaning your engine has to work harder to move the vehicle. This can reduce gas mileage by 0.2% for every 1 PSI drop in pressure across all four tires. Check pressure at least once a month when tires are cold, using the pressure listed on the driver’s side door jamb sticker (not the number molded into the tire sidewall). Proper inflation also helps tires wear more evenly and improves handling.

Replace a Dirty Engine Air Filter

A clogged engine air filter restricts airflow to the engine, which can affect the air-fuel mixture and reduce combustion efficiency. While modern engines with electronic sensors can partially compensate, a very dirty filter can still lower acceleration and fuel economy, especially on older vehicles. Inspect the filter every 12,000 to 15,000 miles or as recommended in your owner’s manual. Replacing a dirty filter is a low-cost, DIY-friendly task that can help the engine breathe easier.

Use the Recommended Motor Oil

Using the wrong viscosity of motor oil can increase internal engine friction. Always follow the oil grade recommended in your owner’s manual (for example, 5W-20 or 0W-20). If your manual allows it, a “fuel economy” formulation of the correct grade may offer a slight additional benefit. Heavier oils than spec can reduce efficiency, while lighter oils may not protect the engine properly. Also, be sure to keep the oil at the correct level; both overfilling and underfilling can cause problems.

Replace a Failing Oxygen Sensor

A faulty oxygen sensor sends incorrect data to the engine control unit, often causing the fuel mixture to run too rich (too much fuel). This directly wastes gasoline and can reduce fuel economy by 10 to 15% or more in some cases. The check engine light will usually illuminate when an oxygen sensor fails. A diagnostic scan at a shop can confirm the issue. Replacing a failed sensor restores proper fuel management and is especially important on vehicles over 100,000 miles.

Keep the Fuel System Clean (Within Reason)

Deposits on fuel injectors can disrupt the spray pattern, leading to poor combustion and wasted fuel. Using a quality name-brand fuel from a high-volume station (it already contains detergents) helps minimize buildup. For most drivers, this is sufficient. If you suspect deposits, a bottle of a reputable fuel injector cleaner added to a full tank can help, but follow the label instructions carefully. Avoid expensive “fuel system flushes” unless your manual specifically recommends them or a technician diagnoses a real problem.

Reduce Unnecessary Weight and Drag

This is not a maintenance item per se, but it complements good maintenance. Items like roof racks, heavy cargo, and unnecessary junk in the trunk increase the load the engine must move. Every 100 pounds of extra weight can reduce fuel economy by about 1%. At highway speeds, an open window or cargo box on the roof creates significant aerodynamic drag, hurting fuel economy more than running the air conditioner in many cases.

Stick to the Scheduled Service

Many routine maintenance items beyond those listed here play a supporting role in fuel efficiency. Fresh spark plugs ensure full combustion. A properly functioning cooling system keeps engine temperature in the ideal range. Clean transmission fluid reduces drivetrain friction. Following the maintenance schedule in your owner’s manual is the single most comprehensive step you can take to keep your car running efficiently and reliably.