What parts of your car affect fuel economy?

Prices for both gasoline and diesel are rising as 2025 draws to a close, and once again, we find ourselves scrambling for ways to save on fuel. But before you consider walking to work, there are several ways to make your car use less fuel on the road.

We’ve already talked about saving fuel through smart driving habits, regular maintenance, and strategies for getting the most out of every fill-up. Now, let’s look at some specific car parts that can affect your fuel economy. If you’ve noticed your car burning through fuel faster than usual, it might be time to check these components.

Before you drive to work, ask yourself if your tires are pumped up to the correct specifications. The reason is simple: underinflated tires make it harder for your car to move forward due to extra resistance from the wider contact patch. Maintaining the correct tire pressure will mean your car’s engine won’t have to use as much fuel to get up to speed. 

The type of tires you buy can also affect your car’s fuel economy. Softer, grippier rubber is great for track days, but it’s not ideal if you’re trying to save money at the pump. Make sure to research the tires you plan to use and consider the type of driving you’ll be doing before installing them.

In addition, regularly checking your tire pressure helps prevent other issues such as blowouts or tire de-beading.

The air filter in your car’s intake system often goes unnoticed, but it plays a crucial role in keeping your engine running smoothly. Its primary job is to prevent contaminants, such as dust and debris, from entering the engine. When the air filter becomes clogged or dirty, it restricts airflow to the engine, leading to inefficient combustion.

In older vehicles, particularly those with carburetors, a clogged air filter can cause a rich air-fuel mixture, which increases fuel consumption. Replacing the air filter at regular intervals ensures that the engine receives clean, unobstructed airflow, helping to maintain optimal fuel efficiency.

If you have a gasoline-powered car, checking the spark plugs for fouling and overall condition is a great way to diagnose poor fuel consumption. Fresh, clean spark plugs ensure efficient and consistent fuel combustion. A failing spark plug can lead to reduced fuel efficiency, engine vibrations, and overall performance loss.

Spark plug replacement intervals vary depending on the material they’re made of. Copper or nickel spark plugs typically need to be replaced around the 60,000 km mark, while platinum or iridium plugs can last up to 100,000 km.

If your spark plugs still have some life left in them, it’s good practice to clean off any carbon buildup on the tip and regap the electrode to factory specifications from time to time.

If you have a diesel car, it likely has an exhaust gas recirculation (EGR) system installed. The purpose of this system is to reduce harmful nitrogen oxide (NOx) emissions by recirculating a portion of the exhaust gases back into the engine’s combustion chamber. This process lowers the combustion temperature, helping to control the formation of NOx pollutants and potentially improving fuel efficiency.

Because the EGR system uses exhaust gases, it can gradually build up carbon deposits over time, reducing airflow and, in severe cases, completely blocking the system. Symptoms of a dirty EGR valve include rough idling, engine pinging or knocking, poor acceleration, decreased fuel economy, and the “check engine” light turning on. If your diesel car is experiencing any of these issues, consider having your mechanic inspect the EGR system for carbon buildup and clean it if necessary.

Another component in your car’s intake system that should be checked regularly is the Mass Airflow (MAF) sensor—unless your car is carbureted. The MAF sensor’s job is to provide the car’s ECU with data on the mass flow rate of air entering the engine. This information helps the ECU determine the correct air-fuel ratio needed for proper combustion.

Over time, the MAF sensor can become fouled with dirt and other contaminants that sometimes make it past the air filter. A dirty MAF sensor can send incorrect readings to the ECU, leading to inefficient combustion and rough idling. It’s a good idea to monitor your MAF sensor’s condition regularly, and a best practice is to clean it whenever you replace the air filter.

A common reason for declining fuel efficiency is a dirty fuel injector. Fuel injectors are small nozzles that spray fuel into each engine cylinder. For proper combustion, the injector must deliver fuel in a fine, even mist that mixes precisely with air.

When an injector becomes dirty or clogged, the spray pattern is disrupted. Inconsistent fuel injection causes inefficient combustion and lower fuel economy. In many cases, fuel injectors can be cleaned to restore performance. However, if the internal components are damaged, replacement may be necessary.

Perhaps the most vital part of your car to check regularly is its oil and other lubricants. Engine oil is often described as the lifeblood of your vehicle. Fuel may power the engine, but oil keeps it alive.

Inside every engine are hundreds of metal components moving rapidly and generating heat. Without adequate lubrication, these parts create excess friction, forcing the engine to work harder and burn more fuel. Engine oil also helps control temperature by carrying heat away from critical areas. Over time, however, oil breaks down and loses its ability to cool and protect efficiently.

Modern engine oils are formulated with detergents and dispersants that prevent sludge and carbon buildup. A dirty or neglected engine cannot burn fuel efficiently, resulting in reduced performance and poor mileage. Regular oil changes keep the internal components clean and ensure that fuel is burned effectively, helping your car maintain its best possible fuel economy.