Diesel used infrequently

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moel

New Member
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Jan 2, 2021
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5
Location
Denmark
Car
W205 - T-model C 250 BlueTEC 2.2
Hi all

My father-in-law, who unfortunately is no longer here, has left my family with a very nice W205 C250 Diesel BlueTEC with only 20,000 miles on the clock.

However, we live in the city and only use the car infrequently. I understand that a modern diesel car should drive long distances, not short ones. Therefore, we use it almost only for the longer trips so it is often left unused for a week or so.

Is it a problem for a diesel car that it is not used more often? Or is it ok as long as we drive long distances when we use it?
 
The theory is that a week or two of short runs should be ok as long as it gets a longer run every couple of weeks to help clean the dpf system and what not.
 
Thanks for the information. Much appreciated.
 
I had a Kia Diesel for 5 years, the car mostly did short journeys, about 1,500 miles annually (apart for the one time I drove it to Paris and back... 600 miles round trip). When I bought it, I raised the issue of the short journeys on a Kia forum, and the advice was to use premium fuels as they burn cleaner and this will protect the DPF. Consequently, I have only ever used premium fuel (Shell V-Power Diesel) in the car while I owned it, and indeed had no DPF issues (or any other issues). That said, Kia cars seem to be more reliable than Mercs, so possibly nothing would have gone wrong with it anyway and regardless of the fuel I used.

Given the low annual mileage of your C250d, using the more expensive premium fuel in it will probably not cost that much more in absolute terms, so it might be a good idea for to do this on the premise that even if it won't help, it won't do any harm either....
 
In my opinion, the DPF regen issue is one you cannot get away from. I think you need to be aware that:

DPF regen is likely to be more frequent after the Mercedes emissions 'cheat software' update.

DPFs are very difficult to predict, as each interval is strongly influenced by the journey types in between each individual DPF regen.

The take it on a good run adage sounds fine in principle, but in practice it will regen when the ECU thinks it's the right time. I've just done a 350 mile round trip. When did it do the regen? After 5 miles of 30mph stop start at the end of the journey, the ECU decided to start a DPF regen as I was reversing it on the drive (I know this because I have installed an indication LED). So now I know the next journey needs a 20 minute uninterrupted run. If I did a series of short journeys, there would be a series of interrupted regens. I don't know about much newer cars, but on the E class w212, this could result in a DPF fault and the need for a new DPF (££££).

When doing a DPF Regen, the exhaust at the exit to the engine reaches 650 degrees C, and consequently DPF regens should really be carried out at above 50mph to limit heat damage to surrounding engine components (namely rubber and plastics). Doing regens round town (because you can't control when they happen), and worse, having interrupted regens when you park up means that the engine bay is being baked. A lot of manuals tell you for a reason that if you get a DFP warning light on the dash you should drive for 20 miles at a minimum of 50mph.

My advice is that either you use the car for infrequent long journeys, and the battery advice further up is good.

Or, if it is going to be used for quite a lot of short journeys, then you should really consider a petrol. I know there's emotional attachment to the car, but short journeys on modern diesels are not well suited.
 
Thanks again for all the comments.
I use my CTEK 5,0 trickle charger once a month to top up the battery. Also I will remember to use premium fuel to hopefully avoid DPF issues.
 
We use several W169 diesels in heavy London creeping traffic without any long term issues with the DPF's over the last 10 years or so. None what so ever! For example, yesterday, we managed to drive only18 miles in one hour, such is the congestion in London!

However, with the W205, we are having some issues with the low mileage despite exclusively using the W205 for motorway journeys only. This is being investigated by our local MB dealership at the moment so I cannot pinpoint the issues. That said, I am concern with the Adblue crystalizing due to a lack of use. Although we have the main battery on permanent charge using a CTEK charger, we regularly get an Aux Battery malfunction error message which often clears within a few minutes of driving, but at least on one occasion, it took 3 days before the error message on the Aux Battery (which is a capacitor in the W205) cleared.
 
That's interesting. My Aux Battery malfunction error message wouldn't clear this September so I changed the capacitor. It's been good since then.
If your local MB dealership can pinpoint the issues with the W205 please inform us :)
 
We use several W169 diesels in heavy London creeping traffic without any long term issues with the DPF's over the last 10 years or so. None what so ever! For example, yesterday, we managed to drive only18 miles in one hour, such is the congestion in London!

However, with the W205, we are having some issues with the low mileage despite exclusively using the W205 for motorway journeys only. This is being investigated by our local MB dealership at the moment so I cannot pinpoint the issues. That said, I am concern with the Adblue crystalizing due to a lack of use. Although we have the main battery on permanent charge using a CTEK charger, we regularly get an Aux Battery malfunction error message which often clears within a few minutes of driving, but at least on one occasion, it took 3 days before the error message on the Aux Battery (which is a capacitor in the W205) cleared.

Well in London you pay the congestion charge and you certainly get some good quality congestion, I do like getting my money's worth...


I think Dpf's are one of life's mysteries nobody will ever understand....At least they can be cleaned effectively if they do get blocked, no need to replace them.
 
Longer runs are not always better. You can be driving for 5 hours, but if it's stuck averaging a relatively low engine speed for that time, the DPF isn't getting heated up.

The key is a good run. Open it up through the rev ranges when it's on the longer runs to blow out the cobwebs so to speak. A good Italian Tune does wonders for a diesel engine.

Key really is - good fuel, regular servicing, giving it the occasional beans.
 
Longer runs are not always better. You can be driving for 5 hours, but if it's stuck averaging a relatively low engine speed for that time, the DPF isn't getting heated up.

The key is a good run. Open it up through the rev ranges when it's on the longer runs to blow out the cobwebs so to speak. A good Italian Tune does wonders for a diesel engine.

Key really is - good fuel, regular servicing, giving it the occasional beans.
Agreed, but the point I was trying to make is that the Mercedes DPF seems a lot less troublesome than some other makes. Certainly, friends of ours living near us, with kids at the same school etc (so similar traffic and driving routes) suffered several DPF failures/replacements on their VW during the same period where we had no issues whatsoever! In fact after 3 DPF replacements in as many years, they ended selling the VW and purchased a Mercedes!
 

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