Hi Dan,
firstly there is some info covering the various bits below in my thread. It's a bit long, you may have to do a bit of searching. But I've also addressed components of your post below.
Since I have been using an OBD scanner, I have been watching the oil dilution percentage go up every few of DPF regens. The regens have been occurring two to three times a week (every 30 - 300 km (ash 33% @ 121K km)! Currently oil dilution is at 7%; in early May I had the oil changed by the dealer, between services due to oil dilution, so the oil is diluting at about 1% per week :surprise: Is this even normal?
Oil dilution increase is normal.
The following is my opinion: However the rate, isn't- regen distance of 30km is way too low unless regens aren't completing or you're doing too much city driving. 300km consistently is borderline too low except in stop-start city driving (in which case the regen won't work properly).
For an explanation of the oil dilution calculation, see
Subdiesel's page here
I have read that at 10 - 15% the DPF light will come on (15% for my 2015 year model?). So when Should I change the oil, or how close to thresh hold 15%, or when from an oil lubricity standpoint?
Change when it reaches the threshold (light comes on) or when you reach the service distance interval or when you reach the service time interval,
whichever comes first. Again
the following is my opinion: The 15% level (was 10% on mine) is simply an extended trigger level to reduce the number of trigger events. (opinion off) Certainly my dealer at one point told us (after checking the oil and resetting the dilution which was at 10%) to keep driving to the next service interval (relatively near) and that it was OK- in spite of the diesel smell from the oil.
Can the % dilution go backwards, say if you do a really big highway drive?
Theoretically yes. Practically, no. Realistically, no: (oversimplification follows) diesel comprises much heavier distillates than the petrol. Diesel components have lower volatility and higher boiling points- higher (200-350C) than the temp to break down the oil, so "boiling off the diesel in the oil" by driving doesn't work the way removing oil dilution by the comparatively volatile petrol may.
I've been buying my fuel at 7eleven, maybe I need to try BP for a bit to see if fuel quality makes any difference to soot buildup?
That may help, however in general (I believe) basically all our diesel comes out of the same stock, with perhaps slightly differing additive packages. Certainly now basically all our petro-fuels are imported, I think the only oil refinery left operating in Oz is in WA (Kwinana, BP). Since our oil is refined in SE Asia we are dependent on their processes and raw stocks (which will define the basic content of the distillate).
One other change I noticed: 'Alpine' diesel seemed to work much better in our 2010 than 'normal' diesel sold elsewhere (and during summer in the high country). However lubricity is affected at high temps with alpine diesel so it's not a good idea to fill with alpine and then around the coast/low country. However as it's winter and if you can and if you wish to test this, drive to a site where alpine diesel is available (even Canberra has it) and fill with a tank of that.
Furthermore I found that the Subaru Diesel seemed, in the early ones at least, to be a bit 'on the edge', i.e. it is intolerant of degradations. To this end, it was specified for EN590 fuel, which Oz was supposed to have, or at least the 'equivalent' thereof which was actually enshrined in legislation. But even the Oz spec fuel was changed, in my opinion, in a rather cunning way: Now since you can't actually circumvent legislation (the law) a new set of values was developed which, if the fuel met, was
deemed to meet the standard in the legislation. So yes, if the standard was 10 but you only got 9, you could be 'deemed to meet the legislated standard'. That way you haven't changed a legislated standard, or been exempted from the legislation (law) but you have changed the physical fuel requirements (otherwise they wouldn't be able to measure them as such...) to your requirements. Somehow, in all these legal niceties, someone forgot to tell the engine to comply with the legal laws rather than the laws of physics and physical chemistry.
Even better: the EN590 fuel standard changes with time. It was limited to 5% biodiesel prior to 2009, that's since been raised to 7%. So an EN590 fuel now (and in the future) may not meet the expectations of an earlier engine.
The dealer oil change cost me $200 I can do if for less than $100 but still I'm not overly excited about the additional cost or time :frown2:
Try a competent independent passenger diesel vehicle mechanic to see if they can diagnose any particular issue. If not driving conditions, it could be any number of things:
- leaky injectors
- faulty sensors
- leaky turbo/intake hoses, pipes or connectors (happened to us)
- faulty DPF / DPF sensors
- etc.
