diesel fuel filter blocking

We’re seeing more and more cases of diesel cars breaking down because of blocked fuel filters in cold weather. And we’d like your help to try and get to the bottom of it.

What’s going on?

In very cold weather, some of the paraffins in diesel fuel form wax crystals that can block the fuel filter, stopping the engine from working. Winter-grade diesel contains special additives to prevent this happening above -15C, but we’re seeing breakdowns due to blocked filters when it’s only around freezing point.

Either the vehicle won’t start or it goes into ‘limp home’ mode. And the cause of this build-up of wax crystals at warmer temperatures is causing a lot of head-scratching in the fuel and motor industries.

Can you stop it happening to you?

It’s not possible to completely prevent the problem occurring, but we do have some tips to minimise the risk:

• Always use diesel fuel that meets standard BS EN590. This will be clearly displayed at the pump
• If you don’t normally cover a lot of mileage, plan ahead so you aren’t using summer-grade diesel in winter
• Petrol stations usually change over to winter-grade diesel around late October to help vehicles run better in colder weather
• Make sure your vehicle’s serviced as per the manufacturer’s schedule, including renewing the fuel filter

We provide 24/7 roadside assistance.

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How can you help solve the problem?

This is such an important issue that the British Standards Institute has set up an industry taskforce to investigate.

Experts from the oil industry, car manufacturers and government have been considering vehicle design, fuel spec, fuel composition, regional differences and operating conditions, to try to pin down the cause. We've supported this by providing frequent breakdown reports to the taskforce, but your experience would be valuable too.

If your car has had a breakdown, and diesel fuel filter blocking was the possible cause, sharing your experience at dieselfilter.org.uk will help the investigations.