Yes, I’ve done a couple of uoa’s on it and will get around to posting them eventually. Fuel dilution was tested by GC. The numbers are at home on another device but fuel dilution was higher in the winter (much more short trip driving in the cold). Oil Analyzer’s Inc tests fuel via GC. You can see some Outback XT examples on the Outback forum. If fuel is being added to the oil, that used viscosity isn’t necessarily from shear because of the added fuel.
My comment about the Subaru Japan oil wasn’t really about them using thicker oil, but more that it’s an oil with a robust ACEA A3 additive pack (typically high ZDDP and high calcium) which most other manufacturers have moved away from in DI engines due to trying to mitigate intake valve deposits and LSPI. Japan also allowed ACEA A3 5W-40 in the FA20DIT.
Good point. Probably not.
Of course, the other thing about high SAPS oils is the fear of intake valve deposits. A highly reputable Subaru engine builder claimed that they saw deposit issues with customer engines running Motul X-cess 5W-40 and now require customers that purchase their built engines to run reduced SAPS Motul X-clean.
Lots of aftermarket Subaru companies got on the walnut shell blasting bandwagon pretty early. Some owners even do it as preventative maintenance. There were a handful of n/a 2.5 Foresters that had legitimate issues with IVD and this was addressed with a TSB. It didn't affect turbo models though.
I could absolutely see fuel dilution as an issue since that is common on direct injection engines. We shall see on the next UOA because that was 3500 miles of that was a road trip from NW IA to DC area, this was on 0w30 AFE. Though it has gotten cold recently so that will probably show up. When I change the oil I try to drive it for about 15-20 min or so, with about 70% interstate.
I haven't seen issues with intake valve deposits on the FA24 yet. There are a handful over 100k. But I believe the FA20's were seeing it under 50k. I only use premium in our Ascent (usually top tier) even though the manual calls for 87, so that should help mitigate the risks of IVD but not sure if it affects fuel dilution. I don't understand how Subaru recommends 87 for an engine with 10.4:1 compression, 14-15psi of boost and in a 4600lb vehicle to run well under load. It never mentions anything about using higher octane when towing or heavy loads, which really surprises me. But the Outback XT and Wilderness both recommend 91 if towing or having higher loads. I don't get how they would be any different?
I believe 0w30 ESP is low SAPs, which would work well for this setup too. Correct me if I'm wrong there. I can't imagine going to an Xw40 oil would be beneficial for this engine unless I was flogging it all the time or tracking it.
Honest question… does a CVT even allow the conditions where LSPI may occur? I’d imagine by the time enough load is placed on the engine to make decent boost, the CVT will have allowed the engine to spin up high enough LSPI isn’t a concern?
The CVT in these are programmed really weird. It tends to keep RPM's as low as possible and locks up the converter very soon. When cold, it will keep RPM up until it starts to warm up, but once it reach about 125F it tries to keep RPM low for MPG. I haven't logged it yet, but I believe it tries to reduce load keep it out of boost or very low levels when accelerating with traffic. There are other annoyances I won't get into about the CVT's programming that are very annoying.
I don't necessarily think the way Subaru programmed the engine/trans as a whole on the Ascent is very good. In temps under 25F or so, it will NEVER reach operating temp if you only drive in town. Once on the interstate there is no issues. When it's 10F or colder, it will reach operating temp on the interstate, but as soon as you pull off and start driving around in town, it goes down and will sit around 160F or so. I did a 100mi trip when it was -5F and even going 75mph it would not reach temp. I've had the dealer look into that and they say it's "normal". I have never had vehicle do this. Heck, my 01 outback will get to temp eventually and hold it in those conditions. I think this is a major reason for fuel dilution in the winter and why fuel economy takes such a huge hit in the winter besides the remote starts. lol I have noticed on colder days when going 70-75 that the MPG meter increases by 2mpg or so once it reaches operating temp. So I would imagine from an emissions standpoint that Subaru would also benefit from revising this and this leads me to believe this is why fuel dilution is an issue. I'm not sure if the Outbacks or WRX's see this happening?
