Is this driving OK with a DPF?

Herzlos

I've seen a Mazda 3 2.2D for sale locally I quite like, and everything looks good apart from it coming with a DPF.

Some of the reviews have mentioned real problems (limp modes and expensive replacements) if they get a lot of short journeys.

My driving is currently as follows:

3-5 short (~1 mile) trips each working day (to train station, shops, etc), one on it's own in the morning and the rest within about 30 minutes of each other, so it should still be a bit warm.

Normally at least one 50 mile A road / motorway round trip each weekend (nearest city) or a slightly longer but still local drive (town or 2 over, running errands).

My driving is therefore about 2/3rd A road/motorway.

My concern is that I don't notice it going into regen mode and finish the trip too early, or that it doesn't see suitable conditions for a regen and sticks me in limp-home mode when on a longer trip.

I know the mileage I'm doing doesn't justify a diesel at all, but it seems to be a fairly sporty car with reduced running costs.

I've heard the regen happens every couple of hundred miles though, so I'm assuming as long as I give it a chance to get up to heat every hundred miles it'll be alright?

OddballJamie

You seem to do less than 100 miles a week. Your short trips will murder a diesel with a DPF. Either walk the short journeys or save your money and buy a petrol car.

Ultrasonic

Also, with doing such low mileage the higher fuel economy of the diesel won't compensate for the purchase price premium on diesel cars at the moment. Buy a petrol. Doing 3,000 miles a year your fuel costs will be pretty small whatever the fuel economy is.

kaya

You do similar mileage to me and I currently run a 3.2 did shogun with DPF, before that I ran a Mercedes c220cdi with DPF ( father in law now runs this car) my mother runs a golf 2.0gttdi which I believe also has a DPF and does less miles, all cars are now averaging around 70,000 miles and none have ever had any problems with the DPF filter , manufacturers specify low ash oil usually for cars with DPF filters and usually the servicing is done with cheap generic oils which clog things up , I get a friend to do my servicing and don't cut corners which is why my cars don't suffer

Indout96

the higher fuel economy of the diesel won't compensate for the purchase price
premium on diesel cars at the moment

I run a 2008 - 2.0 TDI Passat Highline, when i bought it 18 months ago petrol versions were actually dearer and very hard to find.

Herzlos

I know I don't do mileage anything like high enough for a diesel (~5000/year) but I'm trying to find something on par performance wise with my current 2.5l petrol saloon and has a useful towing weight. Most of the petrol cars I can find are pretty sub 1.6l things, offering almost no towing ability and no performance.

I'm not too bothered in terms of purchase price and running costs (it's not much more expensive to buy than the 2.0 petrol and cheaper than the 2.3 mps), but I'm pretty worried about being landed with a £2k replacement DPF bill, or having the car jump into limp mode on the motorway.

In other respects it looks good: reduced tax, insurance, fuel costs whilst providing improved spec, performance, refinement and towing ability.

keith1950

Your weekly 50 round trip should be enough for the DPF to complete a regeneration as long as you keep the revs above 2,500 for at least 12/15 miles.

Its all about the filter getting hot enough to do a regen. otherwise if it doesn't get hot enough it dumps diesel into the oil and tries again until it manages.

If it keeps failing it means your fuel consumption gets worse and it shortens the life of your oil.

OddballJamie

keith1950 wrote: »

Your weekly 50 round trip should be enough for the DPF to complete a regeneration as long as you keep the revs above 2,500 for at least 12/15 miles.

Its all about the filter getting hot enough to do a regen. otherwise if it doesn't get hot enough it dumps diesel into the oil and tries again until it manages.

If it keeps failing it means your fuel consumption gets worse and it shortens the life of your oil.

In a perfect world yes, but that won't happen in real life.

OP is doing 15-25 <1 mile trips in the week and then roughly 2 25 mile trips on a weekend. Worst case is that the car starts the regen 25 times in a week and fails each time, then on the 25 mile trip what if the revs don't stay high enough for 15 miles, traffic, islands, lights, anything could stop it. Then the cycle begins again.

It's a recipe for disaster for the amount of possible fuel savings, which will be minimal due to the 15-25 short trips a week.
You may as well buy the MPS.

This is a worth a read, an owner with the Mazda6 2.2
http://www.honestjohn.co.uk/forum/post/index.htm?t=93840

keith1950

If he definitely wants the car he could force a regen by deliberately driving in 3rd and 4th for his longer trip to keep the revs up.

I agree that this isn't ideal and most people would forget and then run into problems.

Luckily my present diesel doesn't have a DPF and I seriously doubt I would buy one now

gord115

Herzlos wrote: »

I know I don't do mileage anything like high enough for a diesel (~5000/year) but I'm trying to find something on par performance wise with my current 2.5l petrol saloon and has a useful towing weight. Most of the petrol cars I can find are pretty sub 1.6l things, offering almost no towing ability and no performance.

I'm not too bothered in terms of purchase price and running costs (it's not much more expensive to buy than the 2.0 petrol and cheaper than the 2.3 mps), but I'm pretty worried about being landed with a £2k replacement DPF bill, or having the car jump into limp mode on the motorway.

In other respects it looks good: reduced tax, insurance, fuel costs whilst providing improved spec, performance, refinement and towing ability.

I used to run a Skoda octavia vrs (2.0 turbo petrol)and used this for towing,
It was great. The performance will be better than your 2.5 petrol and more economical.
I used to get 30mpg and 25mpg when towing. It also warmed up a lot quicker than my previous diesel.

I personally wouldn't risk a modern diesel,because I too only do low miles(under 4000)

Herzlos

It's certainly looking like I should continue looking at hot hatches (which is a shame as they've probably all been thrashed) and older bigger cars. I currently get about 25-30mpg as it is so pretty much anything will be an improvement :j

keith1950 wrote: »

If he definitely wants the car he could force a regen by deliberately driving in 3rd and 4th for his longer trip to keep the revs up.

I agree that this isn't ideal and most people would forget and then run into problems.

Luckily my present diesel doesn't have a DPF and I seriously doubt I would buy one now

Can you force a regen by running it hot enough for a while?