2019 Subaru Crosstrek 2.0 GDI Motul ecolite 0w-20 15,131km OCI

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136
Location
Whitby Ontario Canada
So I got the UOA back from my wifes cousins car I take care of for them. This car sees 95% highway runs as they live in a rural area and put on 1,000-1,200 kms per week. The way I see it, this is the most optimal operation anyone could possibly ask for. Because of the huge mileage, we decided to leg it out for 15,000 kms and see how it went. They are showing more than 5% fuel dilution, but no abnormal wear metals. Also the way I see it the TBN is still strong at 2.37 as is the cSt at 7.4. Aside from the fuel dilution I'd be inclined to say this is a successful run, but I'm not sure how to proceed. Any suggestions?
 

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Messages
149
Location
FL
The Motul int'l website's tech data sheet shows their 8100 Eco-Lite 0W20 to have a starting 100°C viscosity of 8.4 cSt, so fuel dilution has robbed you of 1.0 cSt. And fuel dilution is red flagged at >5% in your UOA. While the 2.37 TBN is flagged as green, that would be about as low as I would want to go in any OCI. For now your wear metals seem perfectly acceptable, but that can't last forever with that level of fuel dilution going forward. The oil itself is performing quite admirably (more ester content to hold the contaminants than most oils?), but think seriously about reducing the mileage in the OCI's.

The numbers seem to show not enough heat is getting into the oil to volatilise the fuel dilution, and of course, that shouldn't be happening in the first place in a relatively new car with low mileage. Under normal circumstances the standard advice would be to drive the car more and on longer trips so it fully warms up, but since all the mileage is happening on the highway already, that seems rather moot. Perhaps check the thermostat for being stuck open in the coolant system? And research if there are there any TSB's for that car's PCV system, that might be suspect? That's the next place I'd look.
 

STIcandy

Thread starter
Messages
136
Location
Whitby Ontario Canada
The Motul int'l website's tech data sheet shows their 8100 Eco-Lite 0W20 to have a starting 100°C viscosity of 8.4 cSt, so fuel dilution has robbed you of 1.0 cSt. And fuel dilution is red flagged at >5% in your UOA. While the 2.37 TBN is flagged as green, that would be about as low as I would want to go in any OCI. For now your wear metals seem perfectly acceptable, but that can't last forever with that level of fuel dilution going forward. The oil itself is performing quite admirably (more ester content to hold the contaminants than most oils?), but think seriously about reducing the mileage in the OCI's.

The numbers seem to show not enough heat is getting into the oil to volatilise the fuel dilution, and of course, that shouldn't be happening in the first place in a relatively new car with low mileage. Under normal circumstances the standard advice would be to drive the car more and on longer trips so it fully warms up, but since all the mileage is happening on the highway already, that seems rather moot. Perhaps check the thermostat for being stuck open in the coolant system? And research if there are there any TSB's for that car's PCV system, that might be suspect? That's the next place I'd look.

I'll check the PCV system when I have it in next. It's approaching 90,000kms now. I'll change the oil as well as the engine air filter and resample at 100,000kms. It's just terribly hard to believe there is much physically wrong with this car as much as a byproduct of being DI. When they're doing the highway driving they are, a 7500km OCI is a bit unreasonable IMHO. Maybe 10k, but the way this car is driven, it is essentially the picture perfect situation for a DI engine NOT to cause any dilution.
 
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1,790
Location
RI
Fuel dilution is far too high to stretch it out longer. I would keep it at this , or scale it back a little and resample for fuel dilution
 

STIcandy

Thread starter
Messages
136
Location
Whitby Ontario Canada
Fuel dilution is far too high to stretch it out longer. I would keep it at this , or scale it back a little and resample for fuel dilution
I agree. I never considered going linger and I think I'll take it back to 10k and try again. But this car sees way too many miles to do sub 10k oil changes
 
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