Do you know what a dpf (diesel particulate filter) is?  Probably not.  It is a filter fitted to your exhaust to trap particles of soot produced by a diesel engine.  European regulations require one to be fitted to reduce these emissions and it does this job.  It is great for the environment but sometimes not so good for vehicle drivers.

Vehicle manufacturers are supposed to explain to potential customers about DPFs and how to drive to keep them working properly but this does not always happen and, of course, the second or third owner may never get the information.  Customers should be told that if they do a lot of town driving they should buy a petrol engined vehicle.  Vehicles with a DPF will quickly get clogged up on short journeys.

Basically the filter traps small particles of soot.  This builds up in the filter.  When a certain level of soot is detected by the cars sensors the engine management system tells the exhaust to heat up sufficiently to burn off these particles.  This is all done automatically and, unless a problem arises, the driver is unaware of the process.

Unfortunately problems do arise.  A filter blocked warning lamp comes on.  At this point, if you follow instructions given by many manufacturers, you should maintain a speed in excess of 40 mph until the light goes out.  Just try this if you are stuck in a traffic jam or driving in a 20mph/30mph limit.  If the light does not go out you must take the vehicle to a dealer for a forced regeneration of the filter.  This is expensive and usually not covered by the manufacturer's warranty.  We have had this happen to us three times, even when abiding by the manufacturer's instructions.  Now, however, we think that we have the answer and are passing the information on to you.

If your particulate filter light comes on immediately change down to a lower gear so that the car maintains at least 2,000 revs per minute or 2,500 if you can.  If in town this may mean second or even first gear but it is important to keep the revs up.  The light should go out after 6 to 8 miles and the filter will have been regenerated.  This information is not always given in car handbooks. Car manufacturers like to pretend that they do not have a problem with diesel particulate filters but they do.

Buy some JLM diesel particulate additive.  A tin costs 20-25 pounds.  There may be cheaper types but we don't think that they are as good.  You add this to a tank of fuel and it will last for about 6,000 miles.  It works by bonding the soot particles together to make them larger so that they burn at a lower temperature.  This makes your filter less likely to clog up.  As a side effect you may gain a few more mpg. It is hard to be precise but I think that we are gaining 3-4 mpg.  You can buy this at motor accessory shops.  More details about where to buy should be on this site soon.

If your cars warranty has expired buy an extended warranty from Warrantywise.  They will cover your DPF as long as you drive for 20 minutes above 60 mph at least once a week..  They are also a good company to get a warranty from since they cover recovery, car hire and hotel expenses as well as tailoring a plan to your needs.  Quentin Wilson recommends then and we have taken out one of their policies.  Click the link to find out more or phone them on 0800 001 4550.Warranty Wise

If all else fails and you keep on having problems with your DPF there are a number of companies who will remove them and remap your engine settings. Just put DPF removal into a search engine and you will see that it is big business. If you have the filter removed you will not be as green and will be making more pollution but you will not suffer from a blocked filter.  We are told that, at the moment, you don't need a DPF to pass an MOT.  This situation could change in the future though.  Before taking the step of having the filter removed please check with your insurance company because it is a modification to the car and they may want more money from you.

Hopefully, if you put some JLM additive into the fuel, give the car at least one reasonable trip at over 2,000 rpm each week and remember to change down to a lower gear for 6-8 miles should the filter light come on you should not have to visit your dealer with a clogged filter.  If you have to have a new filter it will set you back a couple of thousand pounds or more.

DisclaimerWe've got to do this.  All the information given above is given in good faith and from our own experience but without responsibility.  If you have doubts on any point please consult your main dealer or manufacturer's technical department.

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