DPF Maintenance

This page is intended to give advice on looking after your cars’ particulate filter and  preventing the blocking of a Diesel Particulate Filter (DPF) through driving style and carrying out additional maintenance. If your DPF dashboard warning light is already on, then the DPF system is already blocked and you will need to follow the advice given on  Can I Drive with the DPF Light on. If your DPF is blocking on a regular basis or isnt’ carrying out normal regeneration cycles, then please check out Alternatives to replacing a blocked DPF

If you have a modern diesel car which contains a Diesel Particulate Filter (DPF) then you have to maintain your car over an above the level which an older diesel car demanded. The diesel cars of today contain particulate filter systems (DPF), which, as the name suggests are designed to catch the millions of soot particles, created during engine combustion and prevent them from passing through the exhaust system where they, allegedly, can be breathed in by passing pedestrians leading to associated health risks in some.

Just like any filter, the particulate filter (DPF) rapidly becomes blocked and every few hundred miles, the car computer will carry out a cycle called a DPF regeneration, a process which will burn off the captured soot mass and turn it into very fine ash, which then harmlessly falls into the bottom of the DPF canister – leaving the filter itself clean and ready to capture more soot – and so the cycle continues. Eventually the ash level will reach the point where the DPF system itself has to be replaced, and on most cars this is reached at between 90k and 120k miles, although cars which are driven in heavy traffic or subject to frequent stop – start journeys may require a new DPF at a lower mileage.

The biggest problem with a DPF system, are the parameters required for the car computer to be able to carry out the regeneration cycle and this is largely due to todays modern traffic laden roads, and people who only carry out short journeys meaning that the car never reaches the stage where DPF regenerations can occur, at which point the warning light on the dashboard will illuminate.

Therefore, if you own a DPF equipped car, you really do have to keep on top of maintenance and ensure that the car is serviced on time, using the correct oil and if you don’t use the car for frequent motoway or dual carriageway journeys then you will need to take the car on a ‘regeneration drive’ at least every 300 miles, to enable the car to carry out its vital DPF maintenance.

So, how do you maintain your cars’ DPF System?, an reduce the chances of expensive DPF problems?

Avoid Short Journeys. Well the first is obviously to avoid making short journeys where the car cannot reach its normal operating temperature. The more short journeys you make, the less likely the car will be able to regenerate its DPF and eventually the DPF warning light will illuminate. If short journeys are inevitable and part of your everyday use, then you should take the car on a ‘regeneration drive’ (described below) every 300 miles or so, in order to give your DPF at least one opportunity of completing its regeneration cycle.

Fuel Additive. Use Wynns DPF additive in your diesel fuel. This enables the car to complete its regeneration cycle at lower exhaust temperatures, meaning that a full regeneration can take place in less time and at lower road speeds than normal. The use of this additive is especially recommended when using Supermarket or non premium fuels.

Regeneration Drive. Take the car on at least one 30 minute journey every 300 miles, ideally on a motorway or dual carriageway. During this journey, try to drive in a lower gear at a steady speed in order to hold the car at 3000 rpm, which will increase the engine and exhaust temperature, which are the main requirements of a successful DPF regeneration. If you don’t make many motorway journeys and your car use is generally limited to short trips, then taking a purposeful drive like this, every few hundred miles is a must

Regular Oil Changes.  Regardless of the servicing schedules in your car handbook, you should change the oil every 10k miles. This is because some car DPF regenerations are designed to use diesel fuel injected into the regeneration process, which can sometimes contaminate the engine oil. leading to degredation of the oil quality and in some cases causing the oil level to rise.

Use the Correct Low SAPS oil. Cars with Particulate Filter Systems (DPF) require low ash (LOW SAPS) Oil, this type of oil reduces the amount of ash content produced by the engine and therefore lowers the amount of soot entering the DPF. If you service your car outside the dealer network, then its highly advisable to take along your own oil as many high street garages will not routinely use LOW SAPS oil for oil changes. Using the incorrect oil, not only increases the frequency of regenerations, but may also shorten the life of the DPF.

Clean the EGR Valve The EGR Valve, plays a vital role in a DPF Regeneration as it actively controls the exhaust gas temperature, one of the main parameters which determines when a DPF Regeneration can take place. Unfortunately, the EGR Valve can and does freqently clog and stick eventually on virutally every diesel car due to carbon deposits, leading to lower exhaust gas temperatures which in turn can prevent DPF Regenerations from occuring. I recommend that the EGR Valve is removed and cleaned at least every 20k – 30k miles.

Check the car for problems. In order for a DPF to be able to regenerate, the car needs to reach a certain set of ‘ideal’ running parameters, these include factors such as Engine Coolant Temperature, Oil Temperature and Exhaust Gas temperature, if a sensor fails or a problem occurs with the EGR Valve, Engine Thermostat or even a Glow Plug Failure, then a DPF regeneration may never take place, so it is important to check that the car is operating correctly and any failed thermostats, glowplugs etc are replaced as soon as they are discovered.  A handheld fault code scanner, is a good investment so that you can interrogate the car diagnostic system, to check for other related problems elsewhere on the car, should DPF issues begin. Since a single diagnostic scan can cost between £30 and £50 at a garage, and upto £100 at a dealer, having your own fault code scanner will essentially pay for itself the first time it is used.

City Use and your DPF If you live in London, or indeed any UK City or larger town, then slow journeys in traffic and regular stop – start work during your daily commute are going to be an unavoidable fact of life, and a Diesel Car is probably not the ideal choice for you. However if you already own a car with a diesel particulate filter, then you will need to be even more proactive in avoiding DPF Blockages – which can quickly turn into needing expensive cleaning or even premature failure and require replacement.

For those who live in cities, I highly recommend the use of the CDTI Platinum Plus Additive. This is a specially formulated additive, designed for use in passenger vehicles such as diesel buses and taxi’s used in low emission zone (LEZ) areas, which due to their non motorway use are of greater risk of DPF Blockages – however it can also be used in oridinary cars. The additive works in several ways,  which all combine to actively reduce the soot output of the engine and lower the regeneration temperature of the DPF, which increase the duration between DPF regeneration cycles. By using this additive, you will effectively reduce the soot burden on your particulate filter which will effectively increase the mileage range between the requirement for DPF regenerations to take place – very useful for cars which spend more time in the City than on the motorways.

All of this may seem over the top, but unfortunately the entire Diesel Particulate System was a rushed out, badly engineered solution to the increasingly strict  emissions reduction requirements instigated by the EU which needed to be met by the Car manufacturers.

Diesel particulate systems, especially the early ones are very problematic, and this page is entirely dedicated to giving advice on how to prevent the more expensive problems, which will occur if DPF maintenance is ignored. Non of the above should cost more than £100 – £200 per year to carry out, but will eventually save you the £1000 – £2000 replacement bill, should your DPF fail prematurely and need replacing.