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How to Keep Your Car Running Efficiently and Save on Gas

By Viola Travers · Practical Services & Civic Guide

What vehicle maintenance actually affects your fuel economy

The parts of your car that most directly impact how far you travel on a gallon of gas are your engine air filter, tire pressure, wheel alignment, and engine oil viscosity. A clogged air filter makes your engine work harder to pull in oxygen, which burns more fuel. Underinflated tires create more rolling resistance against the road. Wheels that are out of alignment force your engine to push sideways as well as forward. Using the wrong weight of oil — thicker oil than your manual specifies — creates more internal friction in the engine. None of these problems will necessarily make your car undriveable, but each one costs you miles per gallon.

Other maintenance tasks matter less directly but still add up: a faulty oxygen sensor can throw off your fuel-air mixture, a worn spark plug fires less efficiently, and a clogged fuel filter restricts the flow of gas to the engine. A transmission that is not shifting smoothly keeps your engine running at higher RPMs than it needs to. The good news is that most of these are inexpensive to catch early and far cheaper to fix than the fuel you will waste by ignoring them.

Key Takeaways

  • Check your tire pressure monthly and keep it at the PSI listed on your driver's door jamb, not the maximum PSI on the tire itself — underinflated tires are one of the fastest ways to lose fuel economy.
  • Replace your engine air filter every 12,000 to 15,000 miles, or sooner if you drive in dusty conditions, because a dirty filter forces your engine to burn more fuel.
  • Get a wheel alignment check if you notice your car pulling to one side or if you have not had one in over a year, since misalignment increases rolling resistance.
  • Use the oil weight specified in your owner's manual — usually 0W-20 or 5W-30 — because thicker oil than recommended creates unnecessary engine friction.
  • Have your oxygen sensor and spark plugs inspected during routine service, as worn sensors and plugs can reduce fuel efficiency by several miles per gallon.

Tire pressure: the single fastest way to improve mileage

Your tires lose about 1 PSI (pound per square inch) for every 10-degree drop in outside temperature, and they also lose pressure gradually over time even in stable weather. A tire that is 10 PSI below the recommended pressure can reduce your fuel economy by 3 to 5 percent. The correct pressure is not the number printed on the tire sidewall — that is the maximum safe pressure — but the number on a sticker inside your driver's door jamb or in your owner's manual.

Check your tire pressure once a month using a tire gauge, which costs $5 to $15 and is available at any auto parts store or gas station. Do this when the tires are cold, meaning before you have driven the car or at least three hours after you have stopped driving, because driving heats the tires and temporarily raises the pressure reading. If you find a tire is low, inflate it at a gas station air pump (usually free) or at a tire shop. If a tire loses pressure repeatedly, it may have a slow leak and should be inspected by a technician.

Air filter replacement and engine efficiency

Your engine air filter traps dust, pollen, and debris before air enters the combustion chamber. As it fills up, your engine has to work harder to pull air through it, which means burning more fuel to produce the same power. Most manufacturers recommend replacing the engine air filter every 12,000 to 15,000 miles under normal driving conditions, or every 5,000 to 8,000 miles if you drive on unpaved roads or in very dusty areas.

You can check your air filter yourself by opening the hood and looking at the filter housing — if the filter looks dark or clogged, it is time to replace it. A new engine air filter costs $15 to $40 and takes five minutes to swap out; many auto parts stores will install it for free if you buy it there. Replacing a clogged air filter can improve fuel economy by 5 to 15 percent, depending on how dirty it was.

Wheel alignment and rolling resistance

When your wheels are out of alignment, your tires are not pointing straight ahead even though your steering wheel is centered. This forces your car to push sideways as well as forward, which increases rolling resistance and makes your engine burn more fuel. You might notice this as a pulling sensation to one side when you drive on a straight road, or as uneven wear on your tires (one edge wearing faster than the other).

Have your alignment checked if you notice pulling, if you have hit a pothole or curb recently, or if you have not had an alignment in over a year. A four-wheel alignment typically costs $100 to $200 and takes about an hour. Correcting a misalignment can improve fuel economy by 3 to 10 percent, and it also extends the life of your tires, which saves money in the long run.

Oil weight and engine friction

Your owner's manual specifies the correct weight of motor oil for your engine — usually something like 0W-20, 5W-30, or 10W-40. The first number indicates how the oil flows when cold; the second number indicates how it flows when hot. Using oil that is thicker than specified creates more internal friction in the engine, which means your engine has to work harder and burn more fuel.

When you get an oil change, confirm that the technician is using the weight listed in your manual, not a heavier oil. If you have been using the wrong weight, switching to the correct one can improve your fuel economy by 1 to 2 percent. This is a small gain compared to tire pressure or air filter replacement, but it costs nothing extra since you are getting an oil change anyway.

Oxygen sensors and spark plugs

Your oxygen sensor measures how much unburned fuel is in your exhaust and tells your engine computer how to adjust the fuel-air mixture. A faulty sensor can cause your engine to run too rich (burning more fuel than necessary) or too lean (running rough). Similarly, worn spark plugs do not fire as efficiently, which can reduce fuel economy by 5 to 30 percent depending on how worn they are.

Most modern cars have oxygen sensors that last 80,000 to 100,000 miles, and spark plugs that last 30,000 to 100,000 miles depending on the type. If your check engine light is on, have the code read at an auto parts store (usually free) to see if it points to the oxygen sensor or spark plugs. During routine service, ask your technician to inspect these components and replace them if they are worn. Replacing a faulty oxygen sensor costs $150 to $300; replacing spark plugs costs $100 to $300 depending on how many your engine has.

Transmission maintenance and engine load

Your transmission shifts your engine through different gears to match your speed and driving conditions. If it is not shifting smoothly — if it hesitates, slips, or stays in a lower gear longer than it should — your engine runs at higher RPMs than necessary, which burns more fuel. Transmission problems usually show up as a delay when you accelerate, a whining or grinding noise, or a burning smell.

Transmission fluid degrades over time and should be checked during routine service. Some manufacturers recommend a transmission fluid change every 30,000 to 60,000 miles; others say the fluid is good for the life of the vehicle. Check your owner's manual for the recommendation for your specific car. A transmission fluid change costs $100 to $300. If you notice shifting problems, have them diagnosed by a technician as soon as possible, because transmission damage gets worse and more expensive the longer you wait.

Frequently Asked Questions

How much money will I actually save by doing all this maintenance?

The savings depend on which maintenance items your car needs and how much you drive. If your tires are 10 PSI low and your air filter is clogged, you might be losing 8 to 20 percent of your fuel economy. At current gas prices and average driving, that could mean $50 to $150 per month in wasted fuel. The maintenance itself — tire pressure checks, an air filter, an alignment — costs far less than that in a single month.

Can I check my own spark plugs and oxygen sensor?

You can visually inspect spark plugs if you are comfortable opening your engine, but diagnosing whether they are actually worn requires experience. Oxygen sensors cannot be inspected visually. Have a technician check these during routine service; the inspection is usually free or included in a service package.

What if my car is old and needs a lot of maintenance at once?

Prioritize tire pressure and air filter first, since these have the biggest impact on fuel economy and cost the least. Then move to wheel alignment if you notice pulling, and oxygen sensor or spark plug replacement if your check engine light is on. Spacing out the work over a few months spreads the cost while still improving your mileage.

Does regular oil changes really affect gas mileage?

Yes, but only if you use the correct oil weight. Dirty oil does not directly reduce fuel economy, but it can cause engine wear that eventually does. Changing your oil on schedule keeps your engine running smoothly and prevents the kind of damage that forces it to work harder and burn more fuel.

Should I use premium gas to improve fuel economy?

No. Premium gas is only necessary if your owner's manual specifies it or if your engine is designed to run on it. Using premium gas in a car that does not require it will not improve fuel economy. The best fuel economy comes from proper maintenance, not from a higher octane rating.