So which diesel car has the least DPF problems?. In short, non of them, unless of course you purchase a car which doesn’t have a DPF system fitted in the first place, which will mean buying an older car or a petrol version. The problem these days, is that thanks to the poor reliability of the various bolt on emissions control equipment, diesel cars are simply not covering the taxi like 300k or 400k miles which the diesel cars of 15 years ago were covering trouble free, in fact you are unlikely to get much above 100k miles these days without experiencing potentially expensive problems on a modern diesel car.
At the very least you will be facing a four figure bill to replace the DPF at around 80k – 120k miles, which is when the DPF system on virtually every modern diesel car will reach the end of its design life at which point it will need replacing as part of the normal mileage related service regime, just like a cambelt – but about four times more expensive. Something to bear in mind, and a potential cost which may be required soon if you are looking to buy a used diesel car, with a mileage which is approaching or already above 80k!
In a lot of cases, cars aren’t even getting close to the end of their normal DPF system service life, without experiencing several, often random problems with this unreliable emissions control system along the way, problems ranging from perhaps requiring expensive professional cleaning to premature system replacement at quite low mileages on relatively new cars, DPF’s are simply unreliable and an expensive gamble which many motorists can ill afford to risk, and in a lot of cases its not a case of *IF*, but rather *WHEN* any DPF problems will surface and sour your enjoyment of an otherwise enjoyable car, and when this happens the costs can really mount up, sometimes these problems can be resolved for £300 or £400, only to appear again, several thousand miles later, and require £2000 spending to replace the entire system, it really is that variable and unpredictable, and there are plenty of real life examples on the various owners’ forums.
Since around 2008, effectively we have been letting tree huggers design or rather dictate the design of our cars, rather than engineers and this is where the issues began, and the rushed out introduction of the DPF System was a bit like sticking a band aid onto a gunshot wound. In fact anything which requires the driver to arrange their journeys and lifestyle around the convenience of the car and the green systems fitted to it is bound to be flawed from the start, I mean do you really want to be making trips down a motorway for 40 minutes at a time, every few hundred miles for no other reason than because a warning light has come on?, but basically if you don’t do regular motorway driving as part of your driving style, then this is what you will be doing, so that your emissions control system can effectively service itself!.
DPF equipped cars are basically impractical for anybody who doesn’t do more than 15k miles a year, with most of these being Motorway trips, so if you do mainly journeys which involve lots of traffic lights, roadworks and city or town driving or the car is being purchased to cover mainly short trips like the School run then a DPF will give you problems, and these can be very expensive and will eventually reoccur, even if the system is replaced.
Even high mileage drivers have reported DPF problems on a wide variety of different cars, so the technology is not foolproof, even where the manufacturer recommendations on annual mileage and driving style are followed. DPF’s require a finite set of programmed operating parameters to be reached before a DPF regeneration can occur and this can involve engine and oil temperature, exhaust temperature and the use of the engine glowplugs, and so if a coolant thermostat fails or sticks, or a glowplug doesn’t work then this can quite easily prevent routine DPF regeneration from occurring eventually leading to the DPF becoming completely blocked. Often a minor problem elsewhere on the car isn’t immediately detectable by the driver and so the first inkling that something is wrong is when the DPF becomes blocked, illuminating the dashboard warning light and requiring a dealer visit, in a lot of cases this is where it gets expensive as not all dealer forced regeneration’s are successful and a DPF replacement may be required.
As a car ages, and the miles are accrued naturally the engine loses some of its efficiency, injector nozzles get a little blocked and engine parts become worn, and more smoke and soot will be produced, and so an older car which is producing more soot may require more frequent DPF regeneration’s. Other emissions control components on the car such as the Swirl Flaps and EGR valve may become blocked or stick, and failure of these parts can also lead to DPF regeneration failures.
All of these factors and variables combine to lead to one conclusion, that there is no particular car which is immune from DPF problems, and these can occur at any mileage, in a lot of cases the manufacturers are now treating the DPF systems as consumables and therefore not covered by their Warranty and more often than not, that leaves the driver footing the bill.
I would recommend that you check the owners’ forums and Google for potential DPF issues relating to the car that you are considering buying, i’m sure that you will find that all have more than their fair share of problems and non are immune, whether they are budget diesel brands, or well known German luxury cars. After all, its this kind of research that has led to this blog being produced.
The best advice I can give, is that if you are not willing to pay £1000 or £2000+ to replace what is basically a service item on your vehicle, with no real guarantee of its longevity or when and how often replacement or specialist servicing on it will be required, then avoid a modern diesel car, and instead consider a petrol car or an older non DPF diesel.