Why Is My Gas Mileage Getting Worse?

We’ve all been there, watching the gas gauge creep toward empty and realizing seems to be a bit quicker than normal. Your car should be an efficient machine, so when you notice your gas mileage getting worse, it can be both frustrating and expensive. Often drops in fuel economy come down to simple issues or habits that can be remedied with a little attention, extending your vehicle’s efficiency and saving you money.

In this article, we’ll dive into the most common causes and offer some practical and often easy solutions to get your car running more efficiently again.

Underinflated Tires

Possibly the most common suspect behind poor gas mileage are underinflated tires. When your tires are low on air, they increase rolling resistance on the street. This increased friction means you’ll be using more fuel to travel the same distance.

Check your tire pressure regularly, around once a month or two, and make sure it’s at the manufacturer-recommended PSI. Keeping your tires properly inflated is one of the simplest and cheapest ways to improve your gas mileage, as most gas stations will have a pump where you can top off your tires for a small fee.

Dirty Air Filter

Your car’s air filter plays a key role in ensuring contaminants and debris are kept out of the combustion chamber. Gradually, the filter can become clogged with dust and dirt, reducing airflow and causing the engine to work harder and use more fuel to produce the same amount of power. 

Replacing a dirty air filter is another very simple DIY for anyone looking to give their MPG a little boost. Most manufacturers recommend changing the air filter every 12,000 to 15,000 miles, but if you drive in an off-road or dusty environment, it will likely need to be be replaced more often. A clean air filter will help your engine breathe easier and combust fuel more efficiently.

Worn-Out Spark Plugs

Spark plugs are responsible for igniting the fuel-air mixture in your engine’s cylinders with small arcs of electricity at the tip. When they’re either caked in oil or carbon, damaged, or simply worn out, they can cause poor combustion leading to less power and more fuel consumption. If you notice your car is sluggish, your fuel economy has dropped, or are experiencing a misfire, spark plugs could be the issue.

Spark plugs should be replaced according to your manufacturer’s recommended maintenance schedule. Typically, they last between 30,000 to 100,000 miles, depending on your vehicle’s make and model. Replacing spark plugs can be relatively simple DIY for those who like to get their hands dirty, but they’re also generally inexpensive to have replaced at repair shops.

Excess Weight/Drag in Your Car

We all know that having cargo in your vehicle is a necessity at times, but did you know it could be reducing your fuel efficiency as well? Frequently driving with loaded trunk or roof rack, you could be putting extra strain on your engine, causing it to use more fuel to move the added weight. Cargo-holding accessories like roof racks or boxes also increase the air resistance of your vehicle, decreasing fuel economy as your vehicle fights through the drag.

Clear out your car and remove anything you don’t need. If you’re not using a roof rack or a cargo carrier, it might be smart to remove them as well while they’re not in use. Your car will be lighter and more aerodynamic, which will help improve gas mileage.

Poor Driving Habits

The way you drive has a significant impact on your fuel efficiency, especially when it comes to the gas pedal. Frequent acceleration stop-and-go driving between lights can reduce your mileage, and fast or driving aggressively consumes more fuel. If you’re used to driving in a hurry, you might notice a drop in gas mileage, especially in city traffic where acceleration from a stop is so common.

By improving your driving habits, you’ll likely see an improvement in your gas mileage. To maximize your fuel efficiency behind the wheel, try to drive smoother by easing into acceleration and braking gently. Cruise at a steady speed on highways, and consider using cruise control when possible.

Wrong Type of Motor Oil

Your car’s engine is designed to run on a specific type of motor oil, and using the wrong one could cause a host of issues. If you’ve recently changed the oil and used a thicker or incorrect weight, it could cause the engine to run less efficiently. This is especially true in cold environments where oil can become stuck due to increased viscosity. Thicker oil creates more friction, which means the engine uses more fuel to operate.

To avoid this mistake, especially when changing your own oil, check your vehicle’s owner’s manual for the recommended oil viscosity. If you’ve used a different oil type, you should have it changed immediately to avoid damage and reduced fuel economy. This small adjustment can help improve gas mileage and reduce wear on the engine.

Malfunctioning Oxygen Sensors

Your vehicle uses oxygen sensors located around the catalytic converters to monitor the amount of oxygen in the exhaust gases and adjust the air-fuel mixture to maintain optimal fuel efficiency. If the sensor malfunctions or gets dirty, the engine may end up burning too much fuel (known as a “rich condition”, leading to worse gas mileage.

If your check engine light is on or you’re experiencing a noticeable drop in mileage, a faulty oxygen sensor may be the problem. A professional mechanic can diagnose and replace the sensor to restore fuel efficiency.

Diagnostics & Inspection in Carlsbad, CA

If your gas mileage is getting worse, don’t ignore it. There are a variety of factors that could be contributing to the problem, ranging from simple fixes like inflating your tires to more involved repairs like replacing faulty fuel injectors. The key is identifying the issue early and addressing it before it becomes a bigger, more expensive problem.

At Carlsbad Auto Service, our team of experienced technicians is here to help with all your vehicle’s needs, from routine maintenance to more complex repairs. If you’re noticing a drop in gas mileage or any other performance issues, give us a call or schedule online today. We’ll narrow down the source of the problem and help you get back on the road with the MPG you expect from your vehicle!