blog - why is my mpg decreasing

Why Is My MPG Decreasing?

Nowadays, cars are getting better gas mileage than ever before, and we’re not just talking about hybrids and electric cars. However, after a while, many car owners begin to notice that their miles-per-gallon (MPG) starts to wane. If you have noticed this trend with your ride, today’s blog post is for you. We are going to look at some common reasons why your gas mileage can decrease over time.


Incorrect tire pressure can directly affect gas mileage. Fortunately, this is probably one of the easiest things on this list to change. By periodically inspecting your tires and checking their pressure, you can avoid this problem. If you are not sure how much air pressure should be in your tires, check your driver’s side doorplate — this should have all of the manufacturer’s recommended pressure levels.


Some research shows that bad air filters and oxygen sensors can reduce your gas mileage by a whopping 20 percent. While this may seem too high to be true, it all makes sense once you consider the job on an oxygen sensor, for example. Oxygen sensors help deliver the right balance of air and fuel to your automobile. Similarly, air filters can also affect your intake and, therefore, gas mileage. Thankfully, air filter replacements are fairly cheap and easy to install.


Spark plugs are responsible for sparking combustion in your engine. If your spark plugs are misfiring or not working properly, this can negatively impact your MPG. If you are noticing a decrease in fuel efficiency, check your spark plugs or take your car into an auto repair shop and have a skilled mechanic take a look.


Fuel injectors are responsible for putting fuel into the engine. When something goes wrong with them, this can lead to bad gas mileage. For instance, if there is a leak, less fuel will get into the engine, causing it to run less efficiently.


The type of oil you use can have a significant impact on your fuel efficiency. If you use conventional oil, consider switching to a synthetic or a synthetic blend. This will help reduce friction and improve overall performance. However, before adding a different type of oil, be sure to consult with the owner’s manual and make sure that it is indeed compatible.


As Californians know, having AC in your vehicle is a must. While this can certainly improve our comfort while driving, we must not forget how much of a drain this can be on our gas tank. When the weather gets milder, consider opting for rolled-down windows instead. However, when driving on the highway and at higher speeds, it is actually more fuel efficient to roll up the windows (since open windows create more drag).


While this isn’t something you can pick up at Autozone or even at Shannon Family Automotive (but if you come looking, we’ll try to share a few tips), bad driving habits are a big reason for poor gas mileage. Gas-guzzling habits include accelerating quickly, speeding, and just being an all-around aggressive driver. While it may sound cool to rev your engine at the red light, it needlessly uses up gasoline. Also, while it may seem convenient to keep your car idling while you wait, this is likely unnecessary and a waste of gas.


If you are in the Folsom area and are in need of auto repairs or auto maintenance, we’re ready to help. We are independent Honda and Toyota specialists capable of handling everything from a simple tune-up to a major engine repair. Learn more about us, our auto services, and contact us today to schedule an appointment.

Schedule Your Tune-Up