Motorists usually hear a lot about the importance of replacing oil filters and air filters after a certain time, the oil filters usually more frequent. Not doing so will affect performance as the filter gets clogged up with dirt and the flow of oil or air is affected. In fact, a dirty air filter will definitely cause fuel consumption to worsen.

Just as important is the fuel filter, a small component that also has the task of preventing impurities from entering the engine. This is even more important today with the use of fuel injection in engines where fuel goes through injectors with orifices that are 0.12 mm or twice the diameter of human hair. So even a very tiny piece of dirt can cause clogging which will affect fuel delivery.

Fuel filters don’t need to be changed often and in the absence of guidance from the manufacturer, 24 months or 50,000 kms might be a good interval. However, new vehicles will usually have the interval shown in the manual and the service centre will do the replacement when due.

We are fortunate that in Malaysia, the petroleum companies not only deliver high quality fuel but also have procedures to ensure that the fuel is clean right up to the point of entering the fuel tank. It is usually the fuel tank in the vehicle that will contain dirt and impurities that collect over time and that’s where the fuel filter’s role is vital.

The construction of a fuel filter is actually quite straightforward and consists of high-quality filter media inside a canister which traps particles. Just as with air and oil filters, the quality of the media must be good and reputable manufacturers will use the right materials which can effectively trap tiny particles as well but not affect the flow of the fuel through.

There are filters sold under vehicle manufacturers’ brands which are genuine products and there are also third-party brands (and some of the companies are the same ones that supply to vehicle manufacturers). The ones to avoid are counterfeit ones which will usually have low-grade materials and inferior manufacturing processes. That is how they are cheap but they will fall apart or not filter properly and cause damage to the engine.

Diesel filters (Bosch products shown) have an additional function of separating water from the fuel.

Modern diesel engines have common-rail injection systems that react very sensitively to dirt and water in the fuel. Water, in particular, is bad for performance and there are various systems to isolate the water in the fuel so it does not get to the engine. These systems may work in stages, first stopping dirt particles and then filtering out even the tiniest water droplets.

In recent times, the advent of biodiesel has also made the fuel filter a more critical part of the fuel delivery system in vehicles. Diesel – whether fossil or from renewable raw materials – always contains a small amount of water with nutrients that provide the basis for the undisturbed growth of bacteria and algae. For biodiesel – which has biological ingredients (palm oil), the holding capacity for water is even greater and water separation in the fuel filter becomes even more important.

So if you have an older car, be sure to change the fuel filter regularly. If you have a car which is new and goes to the service centre at regular intervals, with a maintenance schedule being followed, then it is likely that the fuel filter replacement will be specified and carried out at the appropriate time.

[Chips Yap]

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