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2011 Forester Diesel
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Discussion Starter · #1 ·
Hi all,

I started servicing my 2011 Forester diesel at home recently, with oil and oil filter changes every 5,000kms.

Car has 141,XXX kms on it.

I’m noticing that since the oil change, my DPF’s doing regens every 150-160kms. I’m wondering if the brand or type of oil I’m using (Nulon Fully Synth 5w-30 C3 link) could be triggering these unusually regular DPF regens?

This is in contrast to the once every 300kms that the car was previously doing when services were undertaken by Subaru. I’ve based this off Torque telling me that the car has done 460 regens over the 141,XXXkms the car has driven).

DPF seems to be working fine, in that the regens are kicking in exactly when the soot levels are at 65%. The regens are lasting approx. 15 mins, and this brings the soot levels back down to 30% (+/- 3%).

What’s really interesting is what happens after the regen completes. My soot levels always go down further; some times down to 15%-20% within five minutes of the regen finishing.
Then, the soot levels climb back up very quickly. Roughly one percent every couple of minutes. Within a half-hour drive, I’m back at almost 50%.

The car’s being driven, say, 80% of the time doing more than 80km/h with the rest of the time back & forth from the shops. It gets driving in appropriate conditions to regens properly.

Any idea what’s happening here?

Thanks in advance!
 

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2010 Forester Diesel 6MT
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880 Posts
Suggestions:

0) I think the oil 'looks ok on paper' as long as it meets your handbook engine spec.

1) Check for split/leaking turbo hoses, pipes and elbows plus any other possible leaks in the induction system. A common issue with the earlier diesels. The leak may only be obvious under boost- our cracked elbow couldn't be seen until it was pushed open. Your symptoms sound similar to mine.

2) The DPF should go to 0% (or close) upon a regen. In fact it should get there before the 15 mins is up if you're doing the 'right driving' for a regen (i.e. 80+km/h). If it's only decreasing to (say) 30% during the regen then decreasing further as the DPF temp drops (seems to be a common issue on these Subaru diesels- inc mine) there's a good chance (I think) you have and induction leak.

3) Watch your oil level, although if you're changing it every 5k you should catch it before it overfills or over-dilutes.

4) Decarbonising the intake tract may also be something required- you'll need to inspect it for that. Ours was done by Subaru at 100k.
 

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2011 Forester Diesel
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Discussion Starter · #5 · (Edited)
As always, pitrack_1, thank you. So much knowledge and an absolutely legend. I'll check all of that over the weekend and will report back.

Thank you!
 

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2011 Forester Diesel
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Discussion Starter · #6 ·
Suggestions:

2) The DPF should go to 0% (or close) upon a regen. In fact it should get there before the 15 mins is up if you're doing the 'right driving' for a regen (i.e. 80+km/h). If it's only decreasing to (say) 30% during the regen then decreasing further as the DPF temp drops (seems to be a common issue on the se Subaru diesels- inc mine) tehre's a good chance (I think) you have and induction leak.
I remembered something else: during the burn, it's not uncommon for the soot levels to RISE 5% or more when I'm doing 100km/h+. Recently, it started a burn when I was on the way home from the supermarket (doing 60km/h). I navigated towards the nearest 100km/h zone (~ 5 minute drive) and during that 5 mins doing 60hm/h, the burn reduced the soot levels at a more substantial rate than they reduce when doing 100km/h.
 

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2017 Forester 2.0D CVT
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96 Posts
I'm still having issues with the DPF doing a lot of regens. I'm about 135 km between regens doing 15+15km highway driving every day...
I can't see any cracks or leaks in the intercooler hoses, but I don't disassembled it.
My MY16 have 104.000km in the odometer, so the service is close. I will talk to the dealer to do a full inspection of the hoses and lines... This can't be normal at all, specially with my kind of trips. The only reason because I have the Oil dilution controlled is because I use Torque to see the regens and I take the car to the highway to complete them... 30 km extra each time, doing more than 200km each week... do the math with the extra fuel consumption and time loss.
 

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2010 Forester Diesel 6MT
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I remembered something else: during the burn, it's not uncommon for the soot levels to RISE 5% or more when I'm doing 100km/h+.
I think I recall an occasion of that too, but perhaps 1 or 2%, not 5 - except when a regen started over 75%

Recently, it started a burn when I was on the way home from the supermarket (doing 60km/h). I navigated towards the nearest 100km/h zone (~ 5 minute drive) and during that 5 mins doing 60hm/h, the burn reduced the soot levels at a more substantial rate than they reduce when doing 100km/h.
Diverting routes because of a car's behaviour...Don't you hate it when the car seems to be more in control of you that you do of the car! :biggrin:

Unfortunately I thought of a few other things to check that may cause issues.
1) Stuck/blocked EGR/EGR valve
2) Blocked DPF pressure pipes
3) Leaky injectors
4) Oil leaking into exhaust (e.g through failing turbo)
5) Blocked oil breather/PCV (if it exists...)

Some other suggestions to watch for:
a) Changing soot levels with changing DPF temp. For example, do a good downhill coast (if you can) so the exhaust temp drops towards ambient- see if the soot level rises or falls with exhaust temp
b) Rising soot level under coasting that doesn't go away when you resume accelerator driving
c) Differing soot reading upon a cold start (e.g. overnight) after a hot stop.
d) These earlier boxer diesels seem rather susceptible to diesel type or quality. They seem to really like an 'alpine' blend which you'll only find in high (alpine) country during winter.

I'm sorry I'm full of suggestions without any actual solutions! But here's one thing you could possibly try: A DPF cleaner. In our case we used the Penrite one (ignore their blurby ad guff), and under a 'blind' test (my wife) who knows nothing mechanically beyond "the DPF light's on again" (complete urban running unfortunately) after she put a bottle of that in she asked "what was that stuff- it's running like new again". It may be worth a go and see if the soot levels and regen distances behave more reasonably.
 

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2011 Forester Diesel
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Discussion Starter · #9 ·
All very good tips, thank you! Some sound more woeful than others though (failing turbo!!!).

I'll pull the intercooler off this weekend if I get a chance and have a good look at the pipes. From memory, the pipe from the cooler to the throttle body is the likely candidate for cracks, right? Or are all pipes equally as likely.. The pipe from the intercooler to the turbo (drivers side) is a hard plastic pipe with minimal-to-no flex. Cracking doesn't seem as likely there. Or does it?

I did put some LiquiMoly DPF anti clog in last tank and the DPF did the same thing (i.e. stop at ~30%), but in the five or so mins after the burn finished, the soot level reduced down to ~11%, rather than the 20-25% they normally end up at. But then after ~20 mins it was back at 40%, and within another two or three drives, back at ~60%.

Car's doing my head in. Time to trade in and get a non-dpf diesel i think.
 

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1999 Forester S
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When we have issues with frequent DPF regens on vehicles at work, the root cause tends to be excess engine oil making its way into the exhaust tract, coating the DPF. I would keep a VERY close eye on oil levels, maybe even use a bore scope to peek into the exhaust to look for oil residue.
 

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2017 Forester 2.0D CVT
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When we have issues with frequent DPF regens on vehicles at work, the root cause tends to be excess engine oil making its way into the exhaust tract, coating the DPF. I would keep a VERY close eye on oil levels, maybe even use a bore scope to peek into the exhaust to look for oil residue.
Hi!

Please, tell us when you have checked the pipes. I have regens every 120/130km too...

Thanks!
 

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2014 Forester 6 M/T
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79 Posts
Suggestions:




2) The DPF should go to 0% (or close) upon a regen. In fact it should get there before the 15 mins is up if you're doing the 'right driving' for a regen (i.e. 80+km/h). If it's only decreasing to (say) 30% during the regen then decreasing further as the DPF temp drops (seems to be a common issue on these Subaru diesels- inc mine) there's a good chance (I think) you have and induction leak.
Hi pitrack_1, I observing similar behavior from time to time, especially at summer time. You mentioned induction leak, but I'm not sure what you mean. English is not my mother language and direct translation doesn't make sense for me. Could you please explain it a bit for me? Thanks.

Sent from my SM-G930F using Tapatalk
 

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2010 Forester Diesel 6MT
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Hi pitrack_1, I observing similar behavior from time to time, especially at summer time. You mentioned induction leak, but I'm not sure what you mean. English is not my mother language and direct translation doesn't make sense for me. Could you please explain it a bit for me? Thanks.

Sent from my SM-G930F using Tapatalk
Hi svkforester,

what i mean by 'induction leak' is a leak in the air intake system.

In this English case 'induction' does not mean something electromagnetic, this use means "bringing something in." English words can often have multiple uses and meanings.

Now that leak can be pretty well anywhere post ('post' means 'after', not 'mail' :wink:) the air intake measurement device (I'll assume a MAF sensor) and therefore could be in the pre-turbo ('pre-' being 'before'), or post-turbo sections upto the actual cylinder inlet.

My personal suspicion or 'conspiracy theory' is that it's at least partially related to fuel blend as it always seems to happen in summer worldwide when it's not related to some intake pipe failure or loose hose connection. And it's not a matter of buying 'better' diesel, I think the winter blends perform better in these particular early EURO5 engine setups as driving with winter diesel in warmer temps in Oz still had the longer regen periods. It's 'guilt-by-association' though.
 

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2014 Forester 6 M/T
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Thanks for detailed explanation :) I was not 100% sure what it could be but now it is clear. Summer time is hell for at least Subaru diesel engine. This winter I made a new record in distance between DPF regeneration, over 3000km. Even today when spring is coming I have soot level at 61% and last regeneration happens before 1191km. And my Forester (SJ - MY14) has over 100 000km on the clock. May I ask what is yours ASH ratio? I have 42% and I'm not sure whether it is high, low or just as expected. I plan to send DPF for cleaning to specialized company, just as a prevention.
 

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2010 Forester Diesel 6MT
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For reasons I don't want to go into, the DPF has been replaced a couple of times and I don't know what the current ash reading is. However I think outrs was more than 42% and I've heard this is fine. DPF under ideal conditions should last the reasonable life of the car I think, certainly more than 100 000 km.

I wouldn't clean it until it complains about the ash ratio. Especially if you're doing such long distances between regens.

I have a Mazda 3 with 180k km, they are known to have small DPFs and mine hasn't needed replacing (yet).

In my experience it took the second tankful of summer diesel before the winter ('alpine' in Australia) diesel was diluted enough to revert to bad regen behaviour. So if you want to try an experiment, perhaps you could store some winter blend diesel and partially mix it with your summer diesel. The issue with winter blend is the lubricity under high ambient temperatures for the fuel system parts. Also be aware that it's quite likely the Australian winter/alpine blend is similar to a shoulder-season (spring/autumn) European blend, especially where you come from. So you may even be able to use the 'shoulder season' blend (or maybe if you have mountain areas, go fill up there). So you may not need much, maybe 10-15l in 60l to reduce the regen to an acceptable level. All speculation of course!
 

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2014 Forester 6 M/T
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Thanks for the tips and conspiracy :-D. Because here in Europe I can't buy Diesel without bio elements which cause faster fuel degradation I rather wouldn't experiment with mixing winter and summer fuel. Last summer I was happy if I get 200 km or more between DPF regenerations. Usually I was somewhere in between 80-150km. This summer I expect similar behavior. It's quite big contrast between winter and summer and it is quite sad. At the end I think that we can't fix it and Subaru just gave up on Diesel engine so we have to live with this as long as it will be acceptable for us. Currently situation here in Europe isn't good, because of new test, WLPT. Subaru dealers has almost nothing you can buy. You can buy only 1.6i Impreza/XV or 2.5i Outback. I hope that my Forester will last at least 3-5 upcoming years and till then the situation around engines become clear. Sorry for this long post, hopefully it wasn't too boring.

Sent from my SM-G930F using Tapatalk
 

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2010 Forester Diesel 6sp Manual
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Driving around a lot and monitoring cars behaviour I noticed hat EGR stays closed practically all the time when outside teperatures are below +5C. My DPF regens were simmilar to others - 100km summer and ~500km at winter between regens.
Closing EGR at summer practically doubled regeneration range to 200km in simmilar conditions, same route and same fuel.. Apart from fuel type (summer/winter) I'd say EGR also has large impact on soot accumulation.
 

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EGR

Yes from what I have read VW and Mercedes beat the emissions by manipulating the EGR under test condition (Less NOX), then would go back to using less EGR in real world conditions for better performance (bhp) and less problems with the DPF, VW also have their DPF closer to the exhaust manifold so it heats up better and can passively regen easier, also using ad-blue they can reduce NOX and probably rely on the EGR less.

I can't post links so google - THE_STUDY_OF_EGR_EFFECT_ON_DIESEL_ENGINE_PERFORMANCE_AND_EMISSION_-A_REVIEW
The smoke opacity vs load graph shows just how much the EGR effects how much smoke a diesel engine produces, less EGR creates more heat and a better burn/less smoke but higher NOX.

As others have said here an additive like Millers can help.
Some bad people blank their EGR off you will lose a few mpg at low loads as exhaust gas helps make the combustion chamber smaller, but will gain a little mpg at higher loads, you will create more NOX though and if you are caught will face a fine, others have the EGR mapped out but you could still get caught depending on the testing they use.
A good catch can like a provent could be good.
Ceramic coating the pipes leading to the DPF (is it worth it??).
Euro 5 models can get the ECUTEK kit to do forced regens (£300), but your neighbours may not be to impressed if they live close to you with all the smoke.
 

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Hi, has anyone else had any experience with the 30% regen saga? My 2014 ee20 is doing the exact same thing... bulk regens approx every 50 to 60 klm.
Pulled the intercooler off yesterday, pipes looked fine. Fair amount of oil in the cooler which has me concerned.
 
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