Back to all

Mileage Headed Downhill? (What Causes Bad Fuel Economy?)

December 28, 2025

Name someone you know who enjoys spending a lot of money on gasoline.  Yeah, me neither. That’s because it costs quite a bit to keep fueling your vehicle.  

One way to save money on gas is to get good fuel economy, and most of today’s vehicles are designed to maximize your mileage.  But you might find you’re filling up more frequently than you used to and are wondering what can cause your fuel economy to tumble.  Here are a few possible reasons your mileage has been headed downhill.

A logical spot to start is in your fuel system.  You may have a faulty fuel injector or an old fuel filter clogged with debris.  Another problem might be oxygen sensors, which measure the air coming into your engine and the emissions going out. An illuminated Check Engine light may be a sign of trouble there. Plus, worn-out spark plugs can reduce your fuel economy. 

Under- inflated, or over-inflated, tires can also be a cause. Make sure they’re all at the same pressure.  When’s the last time you changed your engine air filter? One that’s clogged and dirty can rob you of better fuel economy. Another bandit is a dirty, leaky, or clogged exhaust system, so have it checked out by a pro.

Finally, how you drive can also mean wasted gasoline. Jackrabbit starts and speeding use more fuel than smoother acceleration.  And if you often sit there with your engine idling while you’re waiting somewhere, you’re throwing fuel away.  Just turn the ignition off.

Try out some of these fuel-conserving habits and they’ll pay off for you in the long-run.

Auto Lab Troy
2790 West Maple Rd.
Troy, Michigan 48084
(248) 643-7690

Need Service?

Request a Quote

More articles from Auto Lab Troy

No Charge (Why Won’t My Battery Hold a Charge?)

April 15, 2026

When your vehicles battery is dead, it leaves you with that horrible, helpless feeling. A dead battery means it wont hold a charge, and there are several reasons it wont. One is age. Batteries have chemical and electrical systems in them that create power, and as time goes by, they wont work we... More

In the Red (Why a Vehicle Overheats)

April 14, 2026

Heat is one thing that can damage a vehicle, especially if a problem isnt taken care of soon. Be on the lookout for signs that its getting too hot in some parts of your vehicle, starting with the most obvious one: the heat gauge/warning light on your instrument panel. When you see that heat gaug... More

Stop! And See Us (Brake Pad Replacement)

March 29, 2026

If youve ever driven a bicycle with hand brakes, youll probably understand how the brake pads on your vehicle work. Bicycle brakes use a system that squeezes the bike wheels rim with a pair of cushioned pads activated by your hand squeezing the hand brakes on your handlebars. The friction of tho... More