Should you buy a car with a DPF?

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frv
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Should you buy a car with a DPF?

Postby frv » Tue Jul 22, 2014 1:29 pm

This seems to keep rearing it's head - this time in the Daily Telegraph.

"For the environment, the Diesel Particulate Filter (DPF) is undoubtedly a good thing, although for some drivers the device has become a source of additional expense and aggravation and a potentially expensive pitfall for buyers of used diesels.

The DPF is designed to catch the diesel exhaust fumes that would usually be emitted in a cloud of black smoke. They've been standard fit on many diesel-engined cars since the start of the century and are necessary to meet increasingly stringent emissions legislation. But they don't like stop-start city driving. And owners certainly don't like the £90-plus bills garages demand to clear clogged DPFs or the £1,000 and more it can cost to replace them.

Like all filters, the DPF gradually becomes blocked. Clogging is prevented by heating the sooty residue and turning it into ash. However, in slow urban driving the exhaust temperatures don't get hot enough for the burn-off, often referred to as regeneration, to happen and the DPF can eventually block.

The first warning the driver gets is when an orange light in the instrument cluster illuminates. One mechanic I spoke to said: "The worst thing you can do is to stop if the light comes on. You need to put your foot down and go for a good blast along a dual carriageway or motorway so the DPF will clear itself." Driving at more than 40mph for longer than 10 minutes should initiate regeneration and solve the problem. Ignore the warning light and things are likely to get more expensive.

It's a conundrum car companies have yet to solve. The AA said: "There's no evidence in our breakdown data that the problem is going away. New models seem just as likely to suffer DPF trouble if not driven 'correctly' as those built when DPFs were introduced." The AA sensibly suggests the answer for drivers who do a lot of short journeys is to plump for petrol and save yourself the DPF palaver.

To add further complication, from February this year any car that is supposed to have a DPF but has had it removed will fail its MoT. I recently heard of someone who bought a used diesel car last summer with 12 months MoT. It failed its latest test because, unbeknown to the new owner, the DPF had been removed.

He was saddled with a £1,300 bill – not quite what he had in mind when he spent £10,000 on the four-year-old car."

http://www.telegraph.co.uk/motoring/gre ... a-DPF.html
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Re: Should you buy a car with a DPF?

Postby Karl » Wed Jul 23, 2014 9:05 am

Great post there Gord.

My troubles with the DPF in my Qashqai was well documented. Even with some lengthy drives it still managed to cause issues and eventually helped me choose another car.

Much of this is down to the design and position of the DPF and exhaust system combined with the start stop nature of many drivers on our congested roads.. Some manufacturers have made changes for the better such as adding a 5th injector to the system and also moving the filter closer to the exhaust manifold. The steps make it easier for the DPF to reach operating temperature and perform a regen but they'll never make the system fail save.

It's been said again and again that you should make sure you take all the factors into consideration when choosing a diesel, however with higher residuals and lower running costs its easy for the vast majority of car buyers to be blinkered.

For more info on DPFs check out our DPF FAQ http://www.hypermiler.co.uk/technical/t ... er-dpf-faq
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Re: Should you buy a car with a DPF?

Postby tighterse » Wed Jul 23, 2014 9:35 am

Of course it's going to be a no choice situation if you want to run a diesel. Over the next few years the non-dpf cars will be off to scrap heap.

My impression, based on not much evidence, is that it's a make and model specific problem. The Quashqai certainly seems to be a horror story but if you look on, for example, the Kia forums it comes across as a minor irritant for some city dwellers. Designers don't learn lessons, remember the original Mini scooping up water or the Cortina with the rattly camshaft.

I also question how much of a problem it really is. O.K. we have AA and RAC comments but as a percentage of call outs how far up the scale does it go? Has anyone looked at statistics from dealers and repair shops?

By all means do some serious checking before you buy a diesel but don;t take newspaper comments as gospel. Papers sell on headlines, not on facts.
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Re: Should you buy a car with a DPF?

Postby frv » Wed Jul 23, 2014 10:42 am

I think you are right TE. I don't hear of too many problems from Kia owners and Merc but even then there are plenty of people on owner's forums complaining that the DPF on their Peugeot, Audi, BMW, Nissan, Vauxhall, Ford is blocked, etc.
I too would like to know the percentage of owners who experience problems. I can't find any specific numbers.
Is it something that generally occurs after you've had the car a while / done a certain number of miles? The DPF's are only supposed to last 65 to 75k miles anyhoo.

A survey on Engine reliability from 2013 found the following:

Top 10 brands according to Warranty Direct

1. Honda (failure rate: 1 in 344)
2. Toyota (failure rate: 1 in 171)
3. Mercedes-Benz (failure rate: 1 in 119)
4. Volvo (failure rate: 1 in 111)
5. Jaguar (failure rate: 1 in 103)
6. Lexus (failure rate: 1 in 101)
7. Fiat (failure rate: 1 in 85)
8. Ford (failure rate: 1 in 80)
9. Nissan (failure rate: 1 in 76)
10. Land Rover (failure rate: 1 in 72)

Bottom 10 brands according to Warranty Direct

1. MG Rover (failure rate: 1 in 13)
2. Audi (failure rate: 1 in 27)
3. Mini (failure rate: 1 in 40)
4. Saab (failure rate: 1 in 40)
5. Vauxhall (failure rate: 1 in 41)
6. Peugeot (failure rate: 1 in 44)
7. BMW (failure rate: 1 in 45)
8. Renault (failure rate: 1 in 46)
9. Volkswagen (failure rate: 1 in 52)
10. Mitsubishi (failure rate: 1 in 59)

Not specifically to do with DPF but I thought it was interesting!

Found this on fleetnews.co.uk:

Driver ignorance could push petrol back up the fleet agenda if problems persist with diesel particulate filters (DPFs).

Car manufacturers say the only issue with DPF technology is that if a vehicle’s exhaust doesn’t get hot enough to burn off the collected soot, the filter can become blocked and a dashboard warning light may come on.

This can be down to repeated shorter trips in an urban/stop-start environment.

The exhaust emissions standards for new cars have effectively required fitment of a DPF in the exhaust of diesel cars since 2009 when the Euro 5 standard came into force.

In fact, many cars registered before 2009 will have had one fitted in anticipation of the change in standards.

The standards aim to deliver an 80% reduction in diesel particulate (soot) emissions, but the technology is not without its problems – AA patrols are regularly called to cars with the particulate filter warning light on indicating a partial blockage of the filter.

Even if an employee’s driving isn’t mainly urban/stop-start, changes to driving style may be required to get the most from these systems.

Mears Group operates around 1,200 vehicles within the M25 and is considering the implications of DPF technology as it considers changes to its van fleet. Fleet manager Jo Hammonds said: “For the larger vans it’s not so much of an issue as you will have to take diesel, but for the car-derived vans do we go for a 1.1-litre to 1.2-litre petrol or a 1.4-litre diesel?”

Hammonds added: “Petrol is very much back on the agenda and I think problems with DPFs will sway policy for us in central London.”

The Salvation Army switched its 750-strong car fleet to petrol in 2010 and fleet co-ordinator Peter Bonney says his DPF problems began with some Euro 4 vehicles that had the technology fitted.

“We understood Euro 5 was bringing them in, but what we didn’t know was to achieve Euro 4 some manufacturers had fitted DPFs,” said Bonney. “Manufacturers were not communicating what the issues were with us.”

Peugeot said its DPF technology – badged FAP – has evolved since introduction in 2001 and was now in its third generation. The system is standard on all 2001-built Euro 4 models as well as newer cars.

A spokesman said dealers had traditionally covered DPF unclogging outside of warranty as a goodwill gesture. This generally involves changing the filter or forcing the vehicle through a ‘regeneration’.

He added that the best solution was to avoid the problem in the first place. “All our literature ensures the customer, either fleet or retail, is encouraged to match the vehicle to their needs,” he said.

“We include a specific section on FAP in our academy training and have an e-learning module on this topic for all customer-facing staff.”

A BMW spokesman said drivers should make a journey longer than 30 minutes each week so the exhaust can reach the optimum temperature.

He added that as the DPF blockage wasn’t a design fault, who should pay for repairs is judged on a case-by-case basis.

“There may be other factors that have an impact on the car’s performance and these would be taken into consideration. It would not be sufficient for any issue to be covered by BMW without question,” he explained.

Volkswagen Group said its brands had carried out extensive training with retailers to ensure customers were made aware of the DPF’s existence and maintenance requirements.

“A large amount of small fleet business is done through the dealer network, so our dedicated fleet sales teams ensure the correct car is sold and the right maintenance available,” said a spokesman.

She added that for larger corporate customers the policy was fleet manager education.

Ford said in the case of a DPF failure it needed to understand the full reasons behind it to decide if the repair could be covered under warranty.

“We have updated our dealer training processes to improve understanding of diagnostic read-outs,” said a spokesman.

Ford has also introduced some tips in owner handbooks to help.

These include warning drivers not to park or idle the vehicle over dry leaves, grass or other combustible materials because of the heat generated during regeneration.

Vauxhall confirmed it “does not pay under warranty” for DPF blockages because there is no defect with the vehicle.

Both Ford and Mercedes-Benz DPFs feature an automatic cleaning cycle.

Renault doesn’t have advice in its owner manuals because it says the customer – both fleet and retail – should have been qualified as right for diesel at the point of sale.

“We will cover the first forced regeneration and after that it will become the customer’s responsibility,” said a spokesman.

“If the forced regeneration is required as a result of another factor not linked to conditions of use, then normal warranty conditions would apply.”

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So it looks like some fleet owners are actively choosing petrol because of the DPF!
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Re: Should you buy a car with a DPF?

Postby Smithsk71 » Sat Jul 26, 2014 10:24 pm

Totally horses for courses and I'm sure I made the right decision with my steady 25 mile each way commute. Have only noticed one regen in 20,000 miles but have never been sure what to look for. Maybe the buildup is very gradual for me - who knows.

I'll be interested to read what mileage people get out of their DPFs to see how long mine might last.

If my job changed and I was quite a bit closer to home I'd probably consider selling it before too many miles went on it and I got DPF troubles. Then ride to work!
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Re: Should you buy a car with a DPF?

Postby frv » Fri Jul 03, 2015 10:38 am

Visitor yesterday came in a rented car, asked him what was up with his car and he said he'd had to get rid of it due to DPF issues. He had a Mazda diesel estate, worth about £6.5 to £7K and the dreaded DPF like started flashing. His wife took it to dealers and they gave her some "strategies" to employ (I'm guessing razz it down the motorway for 20 minutes at high revs! Unfortunately engine management light came on so it had to be towed back to dealers :o
They said as well as the DPF being blocked, the turbo was damaged and it would cost £1500 to fix it all and they couldn't even guarantee the work :roll: so he decided to get rid as it was and only got £2.8k for it.
He did say it was low mileage and he and his wife do mostly short journeys!

He told me he'll never buy another diesel.....
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