Everything You Need to Know About Fuel Filters

March 20, 2025

6 min read

March 20, 2025

6 min read

Older carbureted engines pass larger contaminants (around 40 microns) without clogging. However, modern fuel injection systems contain much smaller orifices and need filtration to 100 microns, even smaller than our eyes can see.

For that reason, many configurations use two levels of filtration. There’s the pre-filter and post-filter system, relating to where each filter is located in comparison to the fuel pump.

The pre-filter, otherwise known as a sock filter, is fitted in the tank. It’s responsible for the majority of the filtration, removing contaminants at the source. However, smaller contaminants can get through.

That’s where external filters come into play. These are located between the tank and the engine and are a second line of defense. The in-tank filter may remove debris at 10 microns, while the post-filter is much finer (100 microns). The in-tank filter cleans fuel at the source, while the external filter deals with fuel coming from the tank to the engine.

Signs Your Fuel Filter Is Going Bad

A young man standing next to a broken-down car with its hood up and holding his forehead. — A clogged fuel filter can ruin your day.

Fuel filters are simple. They have no moving parts and simply act to filter your fuel. It may be surprising how much car trouble you can trace back to a clogged fuel filter. If we think about the three critical elements that an engine needs to run—fuel, air, and spark—a bad fuel filter can knock off the whole balance. After all, it’s a pinch point in the flow of fuel to your engine. If you have a clogged filter, you may experience bad starts or rough running.

Here are the most common bad car fuel filter symptoms to watch for:

Engine stalling: With a lack of fuel getting to the engine, the engine can stall.
Hesitation/trouble accelerating: Without the right amount of fuel getting to the engine, there could be trouble accelerating or hesitation when opening up the throttle.
No-start condition: When fuel can’t reach the engine, it becomes difficult to start.
Reduced fuel economy: As the engine works harder to produce power, efficiency drops.

When to Change a Fuel Filter

An inline fuel filter on an older pickup truck, located on the underside of the vehicle. — The fuel supply lines are secured with two nuts on each side of this older pickup truck’s inline fuel filter.

The fuel filter contains specialized media that traps the impurities in the fuel. However, these contaminants build up in the filter over time, leading to clogs and reduced engine performance because the fuel can’t flow freely.

Because every vehicle is different, figuring out how often to replace a fuel filter requires looking closer at the manufacturer’s specifications. For older vehicles, the fuel filter may need replacing every 20,000 to 30,000 miles, while newer cars can often go 60,000 miles or more. Our best recommendation is to follow the maintenance schedule determined by the manufacturer or change the fuel filter whenever symptoms are present.

Don’t drive with a clogged fuel filter

Once the fuel filter clogs, it’s best to replace it immediately. Inconsistent fuel flow can lead to potential misfires and permanent engine damage, so it’s not worth the risk.

The Ins and Outs of Replacing a Fuel Filter

A mechanic using two open-end wrenches to remove a fuel filter. A shop towel is placed beneath the filter to catch any dripping fuel. — Place a shop towel underneath the fuel filter to catch the gasoline that will leak when the line is disconnected.

The only difficult thing about changing a fuel filter is getting to it. After you have your hands on it, the task is a pretty simple job of unclipping any clips, taking out the filter, putting a new one in, and cursing if you get any gasoline on your clothes. That smell does not want to come out.

Please refer to our detailed step-by-step article and video about how to replace a fuel filter - opens in new window or tab. . Just be aware that things vary by manufacturer and make. Some fuel filters are located under the vehicle along the frame rail or elsewhere under the hood. In most cases, a few common tools are all that you need to replace the filter, aside from the tool to release the plastic or nylon retainer clips.

Typically, users with basic mechanical knowledge can replace a fuel filter within an hour. Internal fuel filters are harder to replace because they are located inside the tank. On some vehicles, you can access the tank and filter through a panel in the trunk or under the back seat. However, it’s rare for these to need replacement.

How much should you spend on fuel filter replacement?

Thankfully, even high-quality fuel filters aren’t expensive. You might spend between $10 and $100 for the filter, with diesel engines costing the most because they use a combined fuel filter and water separator.

If you do the job yourself, you also save on the labor costs, which could be anywhere from $50 to $150 per hour.

Consider Changing These Parts Along With Your Fuel Filter

A mechanic wearing a black nitrile glove installs a new air filter. — Air filter replacement is fast, easy, and inexpensive. If you’re replacing the fuel filter, it makes sense to replace the air filter at the same time.

If you’ve been having engine problems, it can be tricky to determine which part is failing, especially between the fuel pump and filter. It’s not uncommon for drivers to replace the fuel filter only to find out they actually needed a pump. Inspect one when you inspect the other.

When changing the fuel filter, also inspect all of the fuel lines and hoses. These become worn or cracked over time, leading to leaks and reduced flow. If you notice any damage, it’s time to replace them.

Because fuel-filter replacement is considered normal maintenance, it may come at the same time as a complete tune-up. Depending on how many miles are on the engine, it may be wise to replace the engine air filter and spark plugs while you’re wrenching.

About the author

Brian Jones

Brian worked for several decades as an ASE Certified Master Technician in dealerships before starting his used car lot. Today, he writes for top automotive publications including Motor1. In his spare time, he's dreaming of an escape to the country's best trails in an off-road beast.

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This article is meant to provide general guidance only. Automotive maintenance, repair, upgrade, and installation may depend on vehicle-specifics such as make and model. Always consult your owner's manual, repair guide for specific information for your particular vehicle and consider a licensed auto-care professional's help as well, particularly for advance repairs.