2010 STi (E85) - Castrol Edge 0w40 (Euro) - 3,000kms w/shearing

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Jul 31, 2017
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Latest annual test for my Subaru. Yes these OCI's are ridiculously short, I change the oil once a year in September/October and kms are usually only 3-4k. I was tracking some high iron wear a few years ago, but it appears to have worked itself out.

I changed the oil just a touch early because about 1,500kms into this OCI I had a complete flex fuel system installed along with an AOS and custom tuning for E85 and Shell 91. The oil level appeared to drop a little bit, which it has never done before, so I decided to start fresh.

The caw saw a ton of WOT on the dyno, then some more afterwards for follow up e-tuning, then some more just for fun. On E85 the car has about 80-90hp improvement over stock and on Shell 91 it sees about 40-50 hp improvement over stock.

I think all the WOT was probably the cause of shearing the GC in 3,000kms.

I refilled with Rotella T6 0w40 and will continue to change once a year and monitor.

Starting on the left:
GC 0w40 -- Mobil1 Euro 0w40 -- Rotella T6 5w40 -- Motul Xcess 5w40

10STI-200920.jpg
 
Report looks fine, both the 0w40 and 5w40 Castrol offerings usually end up about there although it does not appear to be a problem.
 
It seems the 0W40 oils always end up in the 11s on the boosted 4s....see it all the time with the VW reports.
 
The non-turbo VR6 does the same thing, at least with Castrol's offerings. M1 seems to hold viscosity a bit better.
For sure - I have a 3.6 VR6 in our Atlas that runs the dealer-bulk Castrol 5W40 and it's always sheared down into the 11s each change.
 
I had almost as much loss of viscosity with much less miles in my BMW N52 engine (NA, I6) The car sees mostly short trips so I know that is part of the cause. Maybe it's because there are lot of VII's in this oil?

Not worried enough not to use what I have remaining for my next oil change.
 
Have you guys found the viscosity continues to drop? Or does it remain stable in the 11's for the duration of the OCI?
 
No it settles down. I believe most shearing occurs in the first 1500 to 2000 miles. My UOA at 10k showed 11.4 cst @ 100c, which is about exactly what I've seen on other UOA's in the 5-6k range.
 
OP you think your engine and catalytic converters are fine with a full SAPS like M1 0w40 (in the long run)?
 
Correct me if I'm wrong, but I don't think that would be an issue on this vehicle/engine (ej25)...
- Port injection
- Doesn't burn oil
- Aftermarket high-flow SS cat
- Very short OCIs
 
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