Keeping a low usage diesel healthy

So I’ve just changed jobs to one that’s a ten minute walk to so I won’t be using the car very often, as above it’s a 2011 diesel with 80,000 on the clock bought that I bought two years ago and I was doing around 15,000 miles per year, all long motorway trips, it will now only be doing a few thousand miles per year if that.

I’m wondering if I take it for a thirty mile or so spin every couple of weeks will that keep the DPF from clogging and healthy? There will be a fair few longish trips a few times a year too as family are hundreds of miles away and we holiday in the UK but otherwise it won’t really be going anywhere, the odd trip to the shops etc.

We’re fond of the car and it fits our needs so don’t want to swap it.

Any thoughts appreciated.

Can you avoid short trips, or will it be used for them as well ?  I’ll have a similar issue when I change my petrol car for a van next year. It won’t be used locally, but for trips, biking camping etc so will just get long runs a couple of weekends a month.

The odd short trip but maybe one or two a week max, maybe five miles.

For a couple of years my old polo got very little use. It was a petrol so differences apply but I found that sitting unused wasn’t great for brakes/hand brake and battery I was fortunate that I could park in gear off street to prevent binding but rusting discs were an issue, and costly to replace

An absolute minimum was a proper trip ie 50miles at least a fortnight, preferably more. Motorway and A roads, plenty braking and working hard.

Leaving cars sitting isn’t good long term. Ironically you end up doing pointless journeys to keep them in good order

Non Euro 6 engine? If so, I wouldn’t be too bothered about the low mileage. Much less of an issue on the Euro5 and earlier engines.

If it is a euro 6, find out how often the DPF regens occur, or how to identify a regen is taking place, and ensure the full regen happens

The only way to see if your car is happy or not is to use it and see what happens – the problem being that when DPFs clog/become full then things start to get costly to resolve. Personally I’d sell it and buy a petrol equivalent – modern diesels don’t like short journeys.

Shirley a plug in hybrid is the car for you?
Do the running around on electric the use petrol for the long journey.
Sell the diesel car and use the cash for a deposit on a Kia nero

The only way to see if your car is happy or not is to use it and see what happens…

+1

My circumstances have changed and my Euro6 van has done 3k in the last year. This service will include a timing belt, which is a £££ pain, and I’ll get told about the brakes needing more use, but otherwise it’s mechanically happy.

It does local trips but it gets a run every couple of weeks so I’ll keep it for another 12 months and see how it goes.

It’s a second vehicle and is useful, but to replace it with a petrol car would cost more so it’ll either stay or we’ll go to one car.

No plug in hybrids possible here as we don’t have a drive.

My diesel often doesn’t get used for weeks on end. I don’t use it for short journeys so the DPF isn’t an issue but the stop/start auxiliary battery doesn’t like it. I now leave it on an Optimate to keep it happy which has fully resolved that particular issue.

Nothing else seems to care about being ignored though I expect the tyres would prefer not to be left in the same positions for long term storage.

Nothing special. Just don’t repeatedly stop the engine if mid regen. My 2007 euro 4 relic regens for 15mins every 200miles so it’s easy to predict when it is going to happen.

I rarely drive and have a car sitting on driveway, to avoid making it look abandoned I turn it round every week, ie, park in opposite direction.  On a sunny day I air the inside, spray some gt85 on hinges and check for rodents under the bonnet.  Pump tyres up to 40, disks are minging and need changing.

In covid it did 500 miles between mots, this year c1000 miles max.

We do maybe 5-10 short journeys to every long one in our Euro 5 diesel for last 7 years about 5k miles a year. No issues apart from one exhaust sensor failed a while ago. I think exclusively short journeys is where diesel problems can occur.

Just don’t fret about it. Get it hot once in a while but don’t overthink it.

Thanks for the feedback folks, it appears to be a Euro cat 5 so apparently not so much of an issue, I’ll go for the odd extra spin and see how it gets along.

I wouldn’t worry about it personally.

You’re doing a bunch of longer journeys that’ll most likely deal with most of the DPF regens by normal operation.

Unless it’s something special / high value it’s trade in value is probably in the low £000s at best (from recent experience of similar aged diesel).  So replacement seems like a bad economic decision to me for a low mileage car that is often used for long trips.

My old SMax sat totally unused for three months in COVID and there weren’t any major issues from that.  You might see some battery degradation but that’s likely not much more than £200 to sort out.

If you learn/know what a re-gen feels like then just be prepared to go the long way home from Tesco once a month or go for a quick A road drive to let it finish the job once you’ve dropped off the ice cream.

Plenty of people doing short DMF choking trips sat in cross town or slow moving motorway traffic every day of the week in that generation of car.

Is it the ideal tool for the job?  Maybe not but better the devil you know on older cars so unless you’re going to splash a lot extra you could be buying in a bunch of bills that could very much exceed a replacement DPF.

I had a 2013 Tiguan 2.0 TDI (Euro 5). I bought it 2 years ago with 60k miles. Car was great to drive with full service history and had clearly been looked after. I used it for my daily 25 mile motorway commute until I retired in May this year. Since then it was used very little with just some long holiday trips. In August the eml came on intermittently and then stayed on. The faultccode was relating to the throttle body position sensor. I removed the throttle body and found it was about 50% blocked with carbon deposits! (The throttle body is approx 50mm diameter). Further investigation showed that the inlet manifold was similarly choked. I can only think that this must have been due to too many short journeys in the car’s earlier life. Removing the carbon deposits cleared the fault but left me wondering what other surprises were around the corner.. I have since changed to petrol which now suits my needs better.

It’s a Merc CSL 350, absolutely mint so worth about £7K ish now, it was bought with a proper Merc FSH and everything is spot on so I’ll keep it unless it starts throwing up some monster bills, so far it’s been a few hundred a year in servicing plus some tyres, so doesn’t cost too much to run, especially now I’m hardly ever filling it up.

I would t worry about it. If you were doing daily short journeys then maybe, but op isn’t

Using good quality diesel can help keep engine internals clean (the stuff with added detergents).

Using good quality diesel can help keep engine internals clean (the stuff with added detergents).

The only time I’ve had NoX errors on my Merc Vito was after switching from Shell V-Power to Costco diesel. As soon as I switched back the errors cleared.
Some fuels definitely help keep sensors etc clean.

 I removed the throttle body and found it was about 50% blocked with carbon deposits! (The throttle body is approx 50mm diameter). Further investigation showed that the inlet manifold was similarly choked. I can only think that this must have been due to too many short journeys in the car’s earlier life.

That will be because of the EGR system sending crappy exhaust fumes back through the throttle body.

Just cleaned it out of my Diesel Cayenne – they all have it regardless of usage.

Not using it much won’t hurt it. Doing short trips won’t hurt it. Doing ONLY short trips for a long period of time will.

There are a few different types of regeneration. The car will try to adjust the engine parameters to produce more heat from the exhaust which burns off the soot (passive regen); then if that hasn’t worked it will inject extra fuel after combustion to react with a catalyst in the DPF that heats it up (active regen). For both of these the DPF has to be hot i.e. it has to have been driving for a bit. The active regen also takes some time, 20 mins or something. If you repeatedly stop the car when it’s trying to regen i.e. you’ve driven for less than 20 mins a light will come on and if you’ve read the manual it will tell you to go for a 20 minute drive. If you ignore this, as people must be doing, there’ll be a problem.

However I think Mercedes don’t tell you that they are doing an active regen. So if you continually interrupt this process, you won’t necessarily know. That said, it seems to take a fair old while in a Merc. I have the same car as you (assuming you meant to type CLS) in 250d form which is 4cyl, and I can’t actually tell if it’s regenerating or not. The only hint would be that the start/stop icon goes yellow and stops working; but that rarely happens outside of winter even if I do several weeks of short (8 mile ish) trips. It gets long trips, but probably every few months.

If you are worried, get a diagnostic dongle or app that will tell you the DPF soot load. They can be had cheaply. Oh, and I think this applies to Euro 5 engines as well since they have DPFs.

Re clogging EGRs – the problem with DPF equipped cars is that there can be another fault (leaking boost pipe, bad MAF, bad injector etc) that causes smoke and you never know until something clogs. The DPF may even be able to keep on top of it but the EGR pipe would see a lot of smoke. My Passat didn’t have a DPF so any smoking issue was very apparent; when I took the EGR pipe and cooler off to clean them out I just found a thin film of soot. I cleaned it out and the turbo anyway with Mr Muscle. That bloke who bought it off me had now idea just how good condition it was in :)

We have a 62 plate Quashqui 2.0 dci with 50,000 miles on the clock – all added as short-ish journeys over the twelve years. Never had an issue with it.

I have since changed to petrol which now suits my needs better.

If it’s a direct injection petrol you might have even more soot related problems!

Sell it and buy a petrol?

@molgrips

I use a decent OBD2 Bluetooth adapter and the Car Scanner app on my Vito (OM651).

It can’t force a regen but it can monitor the DPF fill levels and total regens, together with exhaust temps at various locations I know when a regen is in progress. Temps rise up to 650c + from around 200c to 300c during normal driving.

I know on Berlingo’s that people have wired LED’s into the heated mirror wiring as a regen puts the heated windows and mirror’s on to add load (therefore heat) into the engine. If the independent LED is illuminated thateams regen is in action and to carry on driving till it’s finished.

Forgot to mention to the OP – keep an eye on oil levels, failed regens can dump fuel into the sump and dilute the oil. The car is designed for this increase in oil levels but reducing oil viscosity is not a great idea.

Might be timely for me to ask…

I have a 2008 105bhp Golf Match MK5 DSG 1.9TDI 50k on the clock used for daily commute of around 10 miles giving around 55mpg as I drive sedately.

Every so often, maybe once a week or fortnight I pop it in sport and let it hit max revs which produces a spectacular cloud of soot out the back, it only does this once or twice and then it seems the craps been cleared.

Is this a good / useful thing to do to avoid a build up of crap in the engine / protect the DPF?

It gets a long motorway run every month or so, 3hrs X2.

Yes , but you might be better to hold it at high revs , over say 4k for 15 seconds or so . Add a full throttle visit to near the red line as well.
When it’s fully hot , Inc the oil temperature which should be up in the 90s. Which can take 10 miles to achieve

You don’t have a DPF on that car. If soot comes out of the back, there’s no DPF. I would say that the cloud of black smoke is a bad sign anyway. Soot doesn’t really ‘build up’ in a powdery form to be blown out of the back – my guess would be something like sticking turbo vanes so when you boot it, there’s briefly too much fuel and not enough air hence the smoke. And then when it has had a bit of heat in the turbo it unsticks.

I’ve noticed on the app, the DPF fill level drops most quickly when you come off the gas (providing the exhaust is up to temp, so idling at the lights, downhill etc. I guess you’re not adding to the level at this point.

So get it hot, coast, hot, coast is the quickest way to complete a regen.

We have two diesels, subject to different uses (and usually a third, petrol vehicle).

Our Euro 5 van is used occasionally, almost always for long distances.  It’s been with us for 9 years and I don’t think I’ve ever noticed a DPF regen happening, which must mean it’s doing them passively.  We do about 3-4,000 miles a year in the van, so the issues are more to do with corrosion to discs etc from lack of use in the long periods between use.

Our Euro 6 car is used nearly daily, but often for short distances.  I know this isn’t ideal and it’s going to get worse as I have a new car coming early next year (for work mainly).  The new car will also be doing the long distance family-type stuff that we currently use this diesel for and helps manage the much more active DPF regens on this car.  But my wife loves the car and would be very upset if I changed it, so it’ll stay until either catastrophe strikes or it needs renewing with a low-insurance car for the kids to learn on in 2 years time.