Boxer engine 3xUOA: fuel dilution

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7
Location
Quad Cities, IL
Thread starter
Have been tracking my Subaru WReX Premium oil situation because there are so many that burn oil. Clearly my pattern here is dilution so I'm hoping for some guidance on what to do next. Regularly driven in 7mi chunks, which I suspect is the majority of the problem because during the second test I made an effort to take it on longer road trips, rather than just the local, short ones. She is fed PUP 5w30 to keep her in warranty, but that's ending soon. WReX is driven reasonably spirited-ly. Only 3 UOA's done on it attached. No oil burn or loss appears to have started to-date. Here's my thinking on options for next steps. Any others to consider? Can anyone offer an order of preference and reasoning? TIA
  • Drop OCI's to 2k miles and start using really cheap oil. May only change filter every other OCI as well.
  • Go to 5w40 and retest @3k OCI intervals.
 

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14,976
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NE,Ohio
Its a direct injected turbo engine so they can have fuel dilution issues esp in the winter short tripping but yours seems excessive. 7 miles esp in winter is not going to get the oil to temp.. no where close. I'd go with a 5w40 and also try to get it out at least once a week for 30 miles one way. Its basically going to a thin 20wt not ideal for spirited driving with a turbo engine..
 
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24,118
Location
MA, Mittelfranken.de
This is very common with Subaru engines driven on short trips in cold weather, it doesn't seem to have any effects on longevity though. The high copper I suspect is from an oil cooler as lead and aluminum is low which would pretty much rule out main or rod bearings as the source of the copper.
 
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15,226
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N.H, U.S.A.
I'd call subaru about it. Seems excessive for a factory tune. But, Do you have a tune also? If so, tune LEANER. I would move to an ACEA B4 0W30 to get to a higher HTHS. And plan some more HW trips ( at no boost) to burn that fuel off. And Commute the 7 miles at higher rpm / high vacuum reading - no boosting. -Ken
 
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264
Location
Canada, Russia
Possible causes: 1. Low octane fuel causing retarded ignition. Ethanol fuel adds to the problem. 2. Spark plug are not in great condition. Because you normally drive short distances there could be deposits on the spark plugs. 3. A leaking injector. You may want to try a fuel system cleaner before going to diagnostics.
 
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2,399
Location
pa
subaru is relatively new to DI use so their tuning + setup may be an issue, but with many 5-30 fake synthetics being cheap IMO 4 to 5 bucks a qt in 5 qt containers if you intend to keep your ride a while just change oil + filter more often, DIY is cheap! after warranty a switch to a 10-40 would do well unless its a very cold winter
 
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2,161
Location
Arizona
RLI's (Renewable Lubricants) 5W40 was the magic for reducing consumption and fuel dilution in Subaru's turbocharged EJ-25 series. Might be worth a try on these newer ones, too? I can't see the UOAs, though.
 
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2,471
Location
NJ
Originally Posted by bulwnkl
I can't see the UOAs, though.
3 OAI uoa's with one showing 4% and two showing ">5%" via GC. OP at the very least I would be running an ACEA C3 5W-30 or an HDEO 5W-30 like Rotella T6 MV. Also, the owner's manual has hints about thicker oil with 5W-40 on the temp chart and language that a thicker oil is required in high temps. As mentioned, the fuel doesn't appear do be causing elevated uoa wear, although IMO that does necessarily mean that you'll never have an issue. I would definitely give your dealer a copy and ask them to add it to your file. If you dig up the 2015 WRX uoa thread in the Service & Maintenance forum on nasioc, there are quite a few 2.0DIT uoa's there. IIRC, 2-5% fuel via GC isn't out of the ordinary for short trips. Actually, the 2.0DIT forum at subaruforester.org has a sticky with a lot of high fuel uoa's as well. Quite a few of those have lots of idling in winter for warm-ups. Any mods/tune?
 
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Messages
119
Location
Whitby Ontario Canada
Drive it. Alot. At highways speeds without overdrive (6th gear). That car has an oil temp gauge. Get it up to operating temperature and sustain it for at least half hour once a week. Otherwise change it every 3k in the winter and leg it out more in the summer when it's warmer and you're driving more. FWIW, I just did a UOA on my brothers 2017 WRX. 9500KM OCI, Stage 1 Cobb OTS tune. This one is all highway but it's not babied.... [Linked Image]
 
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2,161
Location
Arizona
Originally Posted by bluesubie
Originally Posted by bulwnkl
I can't see the UOAs, though.
3 OAI uoa's with one showing 4% and two showing ">5%" via GC.
That's certainly ‘too much' fuel. OTOH, BSLabs might only report that as "TR." smile Okay, even they would probably figure out there's enough fuel to show a percentage. smile
 
Messages
7
Location
Quad Cities, IL
Thread starter
Just the fantastic feedback I was hoping for all. I'll definitely look for the referenced thread and give it a good read and get the dealer my UOAs. No mods/tunes on this, the wife won't allow it and its hers smile Glad to hear I was on the right track wrt running her on longer trips routinely. And a switch up to something heavier sounds good, I like the Rotella option since I've run that in the past with my race bikes and am familiar. I'll checkout other options in threads too, though. I'll try to return in a year or two with a new UOA andjchanges I made for reference/contribution.
 
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