Has slimer visited your car?

Posted on February 7th, 2014 by Rob Marshall

diesel_filterSome GEM members have experienced problems recently, caused by their diesel cars’ fuel filters (pictured) becoming blocked with slime. The engine becomes starved of fuel and then stalls. Diesel is expensive enough, without sub-standard fuel resulting in a breakdown but media reports, which have circulated since late December, have reported that the fuel is to blame.

More specifically, vegetable-based biodiesel has been reported as the cause. This makes sense to me, because it has been added in greater concentrations, in recent years, to comply with the EU’s Renewable Transport Fuels Obligation. A characteristic is that bacterium thrives in biodiesel and it can breed within a tank, including the fuel lines, and the resultant jelly appears to be the substance that becomes trapped by the diesel filter.

However, in most cases, the small quality of biodiesel that is added to fossil fuel-based diesel tends not to cause any problems. Yet, because of the way that both petrol and diesel is refined and distributed in the UK, it can be impossible to isolate a consignment of ‘faulty’ diesel to an individual petrol station, fuel company, or even to a region. It appears that the Petroleum Industry Association, among others, has looked into the situation and has isolated the problem, judging by the number of reported cases appearing to have dropped over January and early February.

Yet, the long service intervals, imposed by their makers on modern cars, may also have a part to play and many technicians recommend more frequent servicing. Although we endorse that diesel fuel filters should be changed between 12-18 months, many carmakers recommend intervals of 40,000 miles, several years, or longer. Although a blocked fuel filter will starve the engine of fuel, it is doing its job, by preventing the contamination from wreaking further havoc in the more expensive parts of the high-pressure fuel system, which can cost thousands of pounds to repair. Even so, with so many motorists suffering from the problem, we recommend that you specify that your diesel fuel filter is replaced at your next service, especially if you do not cover many miles and the fuel remains in your tank for long periods.