Fuel Filter 101 – Everything You Need to Know About this Auto Part

Cars and car engines have evolved significantly over the past century or so. However, they still run on the same old fuel, for the most part. We made a few tweaks to the petroleum production over time, going from leaded fuel to unleaded fuel, but that’s about as far as significant changes go. However, no matter how good our fuel is today, it still requires filtration. This is why every car out there is fitted with a fuel filter.

What is a Fuel Filter?

There are several important filters on an average car. Most people are aware of the oil filter and the air filter since they directly impact an engine’s performance. A fuel filter is equally important. It’s a device whose purpose is to filter out any debris from fuel, thus preventing the engine from sucking in contaminants into the combustion chamber.

There are two types of fuel filters in use today – inline fuel filter and cartridge fuel filters.

Inline Filters

Inline filters are sitting somewhere between the fuel pump and the injectors. These are standalone units that intersect the main fuel line and are often easy to change.

Inline Filter (Oil/Fuel) (8AN)
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Cartridge Filters

On the other hand, cartridge fuel filters are usually integrated into the fuel delivery system. You could find one as a part of the fuel pump unit or in housing nearby.

Vanos Filter Cartridge
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Dissecting a Fuel Filter

An average fuel filter is very similar to an oil filter. Once you pop it open, you’ll find the filtration medium sitting neatly inside a metal container, isolated by various seals and gaskets. Diesel fuel filters are slightly different since they have dedicated water displacement ports.

Diesel fuel is often contaminated with water, which tends to find its way into your fuel tank and into a high-pressure fuel pump. A diesel fuel filter usually has built-in features that prevent this.

That being said, both gas and diesel filters are only as effective as the filtration medium they come with. The medium’s quality, the number of pleats you get, and several other factors all affect how well the filter will eliminate debris and how long it will last.

Dissecting a Fuel Filter

The Importance of Fuel Filters

The year is 2020. How bad can fuel be, right? You’d be surprised what kind of contaminants end up in fuel these days. You’re looking at anything from contamination that occurred during transport and fuel delivery to the fuel station to the crud that’s been accumulating at the bottom of your tank.

When the fuel pump draws fuel, it forces it through a strainer. This is a preliminary filtration device that picks up any larger chunks of debris. The strainer is primarily there to protect the fuel pump, but it does an excellent job preventing any serious particles from being sent up the lines.

That being said, a whole lot of tiny debris gets through. If you were to pour an ounce of fuel into a transparent cup, you’d barely be able to see the contamination. However, that doesn’t mean it’s not there.

Those super tiny particles are more than enough to clog up your injectors. Look up what a fuel injector looks like, and you’ll notice that fuel is sprayed into the cylinders through tiny holes scattered all over the injector face. Without a fuel filter, those small particles of rust and other contaminants would easily clog up the injectors, causing all kinds of damage.

When Should you Change Your Fuel Filter?

Most fuel filters are rated to last approximately 25,000 miles. Anything beyond that is questionable, and if your filter has passed this point, you should get a new one. Like any other automotive filter, fuel filters will get clogged up eventually. It’s a good idea to stay on top of your maintenance cycles and prevent that from happening.

Symptoms of a Clogged Fuel Filter

When a fuel filter becomes clogged up with gunk, the first thing that often happens is a drop in fuel pressure. The filtration medium is no longer capable of handling the same fuel volume, which ultimately causes the pressure to drop.

Severe cases of a gunked up filter could lead to a loss of power and symptoms similar to a failing fuel pump. Depending on your car and the type of engine it has, you could even trip a few error codes.

The ECU might report that your mixture is too lean since there’s not enough fuel reaching the combustion chamber while you’re still getting the same amount of air.

Symptoms of a Clogged Fuel Filter

Choosing the Right Filter

Filters are one of the most inexpensive parts on a car that also performs a critical function. In other words, there is no reason to cheap out on this car part if you can help it. Cheaper filters feature less effective filtration medium materials. Not only that, but you get less of it.

If you were to take a Mann fuel filter and a cheap no-name brand, break both down and pull out the filtration medium (it comes out as a tape when you unfold it), you’d find that Mann’s is about twice as long. Coincidentally, the same is valid for oil filters and oil filtration mediums.

The obvious lesson here is always to get a new brand name filter. Mann, BOSCH, and many others will work just fine. You might pay a premium for these, but at least you won’t have to change them out for a new one again in 10,000 miles.

All of this is even more important if you drive a diesel vehicle. The fact that water contamination levels are high at a surprisingly large number of pumps, it stands to reason that your filter will probably work overtime. Buy new, buy quality, check periodically, change on time.

Find OEM Quality Fuel Filters

If you’re a proud owner of a BMW, Mercedes, or any other premium European car, you can find quality fuel filters at our online store. We cover a wide range of vehicles as well as filter manufacturers.

That being said, we’ve focused our selection on quality, which is why our inventory is mostly dominated by brands such s BOSCH, Mann, and similar top tier manufacturers. Chose your vehicle from our drop-down menu to find the right parts that fit.



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