UK oil refiners have introduced a voluntary test for their diesel in response to a wave of breakdowns across the country caused by filters becoming blocked by a gel-like substance in the diesel.

UKPIA, which represents the UK refining industry and also has Greenergy as an associate, said its members have introduced a voluntary Filter Blocking Tendency (FBT) limit for diesel fuel to protect consumers. The limit will remain in place until April 15, after which it will be evaluated for effectiveness.

The problem can arise from diesel purchased from any type of fuel retailer and is not specific to any particular vehicle age or make.

It affected a small minority of motorists in the winter before last but the problem disappeared over the summer. However, in November the RAC alone attended almost 600 such incidents.

The problem is not ’waxing’, which used to be an issue in very cold weather, as modern diesel produced for UK winter use is formulated with additives to prevent waxing. The symptoms of the current problem are similar to waxing but the cause appears to be different. And, unlike waxing, when the weather warms up the gel does not dissolve back into the fuel which means a new filter has to be fitted.

UKPIA said it was working with the British Standards Institute’s Task Group, which is investigating the matter.