RAC patrols attended almost 500 diesel vehicles of varying makes and ages after their fuel filters became clogged on Friday (March 2).

The issue represented a significant 5% of the 9,600 breakdowns the RAC dealt with on a day that saw 44% more call-outs than there should have been for the time of year.

Filters appear to have become blocked due to the formation of a gel-like substance in the diesel that leads to the engine being starved of fuel and either not starting or losing power. The amber engine malfunction indicator light might also show.

The cost of a garage replacing a clogged diesel fuel filter could be as high as £200 depending on the vehicle, says the RAC.

RAC fuel spokesman Simon Williams said: “The RAC last saw issues with diesel ‘waxing’, as it is known, predominantly in the east of the UK in the very cold weather of late 2013, and to a lesser extent in periods of really cold weather since then.”

Williams told Fleet News that his should not occur as all diesel produced for UK winter use is formulated with additives to prevent waxing.

“In addition, modern diesel vehicles are fitted with heating elements on the fuel delivery lines to prevent waxing occurring,” he said

“We are, however, aware that some vehicles’ fuel lines are more exposed than others which can exacerbate waxing issues.”

The problems seen in late 2013 led to a working group being set up to investigate the cause.

The RAC is an active participant along with other breakdown service providers, motor manufacturers and representatives from the fuel industry.

“Frustratingly for motorists, however, there is still no solution to this problem,” continued Williams. “The most likely explanation appears to be that there are a combination of factors at play involving the diesel itself, its bio content, and the way vehicles move the fuel around their systems.

“Unfortunately there is nothing diesel car drivers can do to prevent the problem from occurring other than getting their vehicles’ fuel filter changed in line manufacturer guidelines and keeping their car in a garage if they can. Even then, this may not stop a problem happening out on the road.”

As a member of the working group set up across the industry to get to the bottom of this issue, the RAC says it is working hard to amass and analyse its breakdown data to help find a solution.

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