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8 Main Causes of Bad Gas Mileage and What to do about It

8 Main Causes of Bad Gas Mileage and What to do about It

Are you wondering about why your car gas mileage got worse?

A few years ago, you might have been driving around in a car that got 28 miles per gallon on the highway. But as time goes by and more cars hit high-mileage milestones such as 100KM or 200kMs (or even higher!), some people may be left to wonder why their gas mileage is getting worse while they drive off into the sunset with less fuel efficiency than before? It’s all thanks to an EPA-certified vehicle rolling out at 20 MPG instead of what it was rated initially.

Your car is aging and you have noticed a drop in gas mileage? This could be due to many reasons, but it is important not just to fix the symptoms. Read on for tips (regarding what causes bad gas mileage) that will help get your vehicle running smoothly again so you don’t need anything else!

A few different factors can impact how efficient an older vehicle operates including dirty air filters or clogged up cartridges – which have been known causes before as well as now by the latest advancements.

Read on the article to find out about the main reasons that lead to the bad gas mileage. Let’s start!

8 Reasons that cause Bad Gas Mileage in Vehicles

Incorrect Tire Pressure

One of the foremost reasons that cause bad gas mileage is incorrect tire pressure. If you find that your car is not getting the gas mileage it used to, there’s a good chance incorrect tire pressure may be responsible. It can also cause other problems like shakes and hard starts when turning on ignition at stoplights or while driving in traffic jams- which might make for an unpleasant drive.

A low PSI doesn’t just reduce performance though; pumping up those tires will get rid of these issues as well so don’t skip this important service too soon after purchase. It is always recommended to check your own air levels before trusting them blindly under-inflated versions from auto stores because they often overinflate themselves without knowing.

Old Engine Air Filter

Your car’s engine needs air to breathe. When the filter becomes clogged or dirty, it will not be able to get enough and as a result, older engines may have worse gas mileage because they are trying their best but can’t do anything about it while newer cars typically won’t suffer any performance degradation at all even if there is an issue with your fuel injection system which I’m sure you’d want to be fixed so that doesn’t happen in case something like this ever happens again.

Engines that rely on carburetors are more likely to experience the problem with their air filters. The engine owners should check the owner’s manual or have it serviced at an oil change around 15,000-30K miles in order to avoid problems like these from occurring and ensure proper engine performance throughout its lifetime.

Bad fuel injectors

Bad fuel injectors can also cause bad mileage. This is because the fuel injection system, which consists of several components to make sure you always have enough gas in your tank and it’s being put exactly where we need for combustion efficiency–running low will eventually lead to worse performance no matter what kind of car engine or model year vehicle this may be affecting.

Dirty Oxygen Sensors

With the invention of oxygen sensors in 1996, cars have been getting more efficient. There’s no longer a need for carburetors as fuel is now fed to an engine from its computer-based on how rich or lean exhaust gases are outside and what O2 sensor readings show up inside; this means less wasted gas.

A dirty oxygen sensor, which is one of the most common causes for a check engine light and may need inspecting or even replacing before your vehicle reaches 100k miles. These sensors are relatively affordable to replace helping you save on gas while keeping emissions in check.

Bad Driving Habits

Your driving habits can make or break the mileage you get out of your car. If you are an aggressive driver, this means that when it comes time to accelerate and take off from a stoplight as quickly as possible in order not be late for work because nothing slows us down like responsibility – well… That may very well wear down components such as gas efficiency.

The same goes with revving up on hills; again This might sound cool but really all too often people do these things without considering how much fuel consumption their actions will cause them at higher speeds where less traction is available due simply by being unable to generate enough force through the engine.

Shabby Piston Rings

Your engine’s pistons are equipped with rings that create compression to push air and fuel into combustion. If these wear out, it can affect the efficiency of your car because they aren’t doing their job as well in making a seal against cylinder walls for higher pressure levels which results in less efficient power production from turning grains of oil on an internal combustion process. A good idea is always changing up what type you use within the owner’s manuals (even if it is recommended).

Misfired Spark Plugs

Your spark plugs are like the heart of your engine. They make sure that combustion happens when you need it, and if they misfire or aren’t working properly then this can affect how efficient gas use is for a negative amount.

Clogged Mass Air Flow Sensors

The mass airflow sensor on your car’s engine is a crucial device that keeps track of how much air enters the bay, as well as when to inject more fuel. If these sensors become clogged or dirty with debris from outside elements such as rainfall-driven weather patterns then it can cause serious problems for both efficiency and stability in an otherwise normal running vehicle


The above-mentioned reasons might be the ones that cause bad gas mileage for your vehicle. Keeping in mind these, you can take preventive and safety measures accordingly.

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