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Discussion in 'General Discussion' started by tanuie, Apr 24, 2014.
Are diesels suitable for short local journeys?
If they have a DPF [ diesel particulate filter] fitted - and all new diesel engined cars have- then short journeys which prevent the engine and exhaust system from reaching operating temperature mean there is no chance for the DPF to " regenerate"-- that is burn off accumulated particulates- eventually this leads to the DPF blocking or partially blocking meaning reduced fuel efficiency or at worst engine damage. The driver is normally alerted before this by some form of warning on the dashboard. -- Provided the diesel owner is prepared to drive the car for a long enough distance / period of time to regenenerate the filter on a regular basis then this should prevent this blockage occurring Mercedes recommend a 30minute trip every 300 miles If this regime doesn't fit with the cars normal usage and factor in the increased price of diesel fuel then petrol may indeed be a more logical choice.
Thanks for the reply. I was looking at 2006 cars, does this have a DPF, if not what would be the consequence. I don't see a problem with a 30 minute trip every 300 miles if need be with a DPF fitted.
There was a "period of transition" around that time where some cars were fitted with them and others not. Depends on the model and make. Without visual inspection or the chassis no it's impossible to tell. Have a search on the forum on the subject- lots of posts about this. I'm guessing a 2006 uk car won't have a DPF.
But, why would you want one ?
I guess there is a case for liking how they drive or maybe a requirement for more torque than an equivalent petrol - but in a regular short journey scenario, a small engine petrol would make more sense.
IIRC diesels take longer to warm up, too.
Diesels do take longer to warm up.
There is less waste heat with an efficient diesel engine.
Many (maybe most) taxis are diesels.
Is the W642 BlueTec diesel fitted with Urea injection and a DPF? Or is the urea injection enough so that the DPF isn't needed?
There's an inference that diesel is the wrong choice for low mileage users, and this argument always raises its head in the petrol/diesel low mileage discussion.
My car is a 2010 E350 CDI 265 bhp Avantgarde with some extras, which I bought from a main dealer for £23,000 at 2 years old with 8,000 miles on the clock and in showroom condition. VED is £175 a year and my latest insurance premium was £300. It does 0-60 in 6 secs top speed is 155 mph and it does 50 mpg 'on a run', according to the computer. (I've never been interested enough to check by any more accurate means. If consumption was an issue, instead of buying a big car and mythering about how much gas it's using, I'd have bought a Fiesta). I've put 7000 miles on the clock in 16 months. I've had one DPF issue in 5 years of diesel ownership, which was cleared with a short Sunday morning run up the motorway.
If any diesel detractor would tell me which petrol engined Mercedes fulfills all the above criteria, but would have been a better buy and cheaper to run, I'm all ears and willing to revise my decision making processes.
Local MB specialist recommended my dad not to go for the new CDI engines in the W212 and W204 facelift, after he asked about the viability of buying a 350 CDI for city driving. The chap said they have countless MB owners coming in with these cars for DPF regeneration or replacement.
Im really thankful for him to be honest and that's why my dad has got a 2008 W221 CDI instead, since the DPF system fitted in this model is more 'reliable'..the chap said that they hardly come across DPF problems in the W221 320 CDI and they get alot of them for service etc...
He was saying that one of his customers bought a W212 facelift 220 CDI, brand new, who travels 3 times a week on the motorway due to work and the Dpf is still not being able to regenerate, causing it to get blocked.
Glad I don't have a dpf
Is it possible to see when the car is regenerating the dpf? I've never been aware of any dpf problem so I assume all is well, but it would be good to know for sure.
I believe the exhaust system in the V6 diesels is more sophisticated as it has to incorporate the Mercedes Adblue urea injection system to minimise NOx emissions. It consists of a Diesel Oxidation Catalyst (DOC) followed by a NOx Absorber Catalyst (NAC) followed by a Diesel Particulate Filter (DPF) and then finally the Selective Catalytic Reduction (SCR) catalyst. I can only surmise that the NAC stage helps keep the DPF clean. Adblue was first introduced to the V6 engine because that was the powerplant of choice for the USA and several states required low NOx emissions before the cars could be used there. Hence the difference, altho its not entirely clear from this explanation.
How the Mercedes-Benz BLUETEC System Works
It's only a matter of time before this low NOx technology begins to be introduced in Europe which hopefully means less DPF problems for the 4 cylinder engines too.
ps I suspect that many DPF problems may arise from owners not using the correct LOW SAPS [ low ash residue] oils at service time.
How about a 2001 C320 petrol, cost £3000 and gets 25 on my commute in London and 30+ on the motorway. Ok, its not mid 7s for the 60 time, but I'm still nearly £20000 behind you. How about that for a petrol to convince you?
Just to add based on observations I made over the last couple of years. A lot of the moms at my boys school that have diesels and are only doing the school run have been facing issues int he last couple of years where the cars where new and with DPFs. Cars range from X5/X3, Q5 , A3 and a Porsche diesel plus a Jaguar. All of them were down to DPF. What they all have in common is a short trips under 3-4 miles twice a day...
Also interestingly our neighbours brand new Jaguar XF diesel started having DPF issues within less than a month due to the fact that she only does school run and other short trips. Also a colleague who leaves in Chiswick bough recently a second hand A6 diesel with DPF and because he only does short trips within 3-4 weeks he told me he got a warning and ended taking the car on the motorway just to regenerate the DPF
On the other hand my other neighbour with a C220 Diesel has no issues but does long trips many times a week..
Diesels are great if your driving involves longish motorway trips but in my opinion not suitable for short runs. That was the decision criteria ordering our new car . the B180 SE petrol is more suitable for my wife's driving rather than the diesel equivalent even if the later has much better fuel economy. The last thing I want is to keep asking her on a weekly basis if she has taken the car on a longer trip to regenerate the DPF.
So as always not one size fits all
Not sure whether your comment is a serious contribution. I acknowledge the validity of your philosophy, but it's a bit of a cop-out in relation to the discussion. To be fair, in order for my query to be answered it has to be on a like for like basis in terms of the age and model etc. of the car. No one would argue against the fact that buying an older, cheaper car would reduce motoring costs overall - ignoring any additional maiintenance costs due to its age. My comments were in relation to a comparison between diesel and petrol cars of similar age and class. A diesel and a petrol side by side.
For your response to carry any weight you would need to make a comparison between your car and a 2001 C class diesel.
Is my 2012 C350 CGI Sport saloon a good enough comparison then? VED is £175 a year (same as yours) and my latest insurance premium was £237 (£63 less than yours). It does 0-60 in under 6 secs, top speed is limited to 155 mph (although I've only ever taken it to 150mph) and it does nearly 40 mpg 'on a run, using cheaper fuel. I've NEVER had any DPF issues in 50 years of motoring. My car doesn't sound like a bag of nails when I start it up and it has a far flatter power curve that suits me better than the sudden drop off of a diesel.
As Theo said earlier, there's not a one size fits all. We choose what suits us, or at least we should.
The good thing about having a dpf is you never have to clean inside the exhaust tips
Ok, seems reasonable, even if your car is a rarity. But mine doesn't sound like "a bag of nails" either, and nor is there any sudden drop-off of power - at least not up to any speed that I've driven it at, and I'm not sedentary. Insofar as these latter two comments are concerned you may be passing judgement based on lower-end or older cars. Young lady down the street has a new Juke and that sounds like a bag of nails when cold, although it's not unpleasant to my ear.
"As Theo said earlier, there's not a one size fits all. We choose what suits us, or at least we should." - what suits us, or what we want; there may be a difference. My first post on the subject was aimed at those who seem to think that their logic, and arithmetic, should be applied to everyone else's choice. I tend to make up my own mind.