2021 Subaru Outback 2.5L / Amsoil Signature 0w-20 4.9k miles

Here’s my results for the Subaru Outback Limited 2.5L Direct Injection NA engine. It had roughly 4800-4900 miles at sampling. Amsoil Signature 0w-20/ Wix filter. Oil was changed last September and sampled this March. This vehicle is used for roughly 4 miles daily commute round trip in Minnesota. I’m quite surprised at the fuel dilution percentage. During the very cold winter days remote start is used and we try to limit it to 5 minutes or less. I’ll be changing the oil soon and resampling in 3k miles. I’m thinking it has to do with the overall boxer engine design. Nonetheless the oil viscosity held up great.
Bout normal fuel dilution for a fuel diluting Subaru GDI engine. I see around 4% fuel in my '22 Crosstrek at 3,000 mi. For that reason and for piece of mind, I do 3000 mi OCIs with this vehicle.😎
 
Carry on! Going to 10k before changing? As others have said a highway drive at engine temperature would help a bit with your fuel dilution.
Not the case with my '22 Subaru Crosstrek. Had a 600 mile road trip at speeds averaging 65-75mph and still saw 4% fuel at 3000 miles. There was another guy on here with a WRX I believe and he commutes 70 miles a day on the freeway and still had 5% fuel at I think 5000 miles. I'm not buying the theory that freeway driving will help. At least with a Subaru GDI engine anyways. You'd have to be nuts to go 10k with a Subaru GDI engine. Oil is cheap. Change it more often. Not my engine though....
 
It would be interesting to see if a plug in block heater would help with the dilution (assuming you do not have one) as well as eliminating the need to warm the engine.
Doubtful... My Subaru sits in a heated garage when not in use and I still see plenty of fuel dilution.
 
Amsoil oil is overkill in my mind for your usage. NAPA synthetic 0W20 is all that is needed.

Unsure of the need for a UOA unless your going to push the OCI.

Fuel dilution is not great in a gas engine.
Try using a fuel cleaner every oil cycle and see if it helps
In my '22 Subaru Crosstrek, I use Redline Fuel System Cleaner every oil change and have 3000mi OCIs and do many "spirited" highway driving sessions during this time and it does not care one bit. Fuel dilution is high like other Subaru GDI vehicle owners. Maybe this works with other GDI vehicles, but not in Subarus from what I have seen.
 
I think the OP needs to take the "long way" to work once a week in the winter. Get the engine to full operating temp and drive it for 15 min. A 5 min commute in the winter in Minnesota is not going to get it warmed up. You may not eliminate fuel dilution but may cut it back in the cold months by following my suggestion.
 
Not the case with my '22 Subaru Crosstrek. Had a 600 mile road trip at speeds averaging 65-75mph and still saw 4% fuel at 3000 miles. There was another guy on here with a WRX I believe and he commutes 70 miles a day on the freeway and still had 5% fuel at I think 5000 miles. I'm not buying the theory that freeway driving will help. At least with a Subaru GDI engine anyways. You'd have to be nuts to go 10k with a Subaru GDI engine. Oil is cheap. Change it more often. Not my engine though....
Here is this UOA that at least gives some hope... I'd like to know the driving habits during this run:

https://bobistheoilguy.com/forums/t...11-miles-2021-subaru-forester-limited.359847/

Viscosity, flashpoint, and fuel % (I understand people say BS Labs runs low on that) all look good on a 6k mile run of 0w-20...
 
Not the case with my '22 Subaru Crosstrek. Had a 600 mile road trip at speeds averaging 65-75mph and still saw 4% fuel at 3000 miles. There was another guy on here with a WRX I believe and he commutes 70 miles a day on the freeway and still had 5% fuel at I think 5000 miles. I'm not buying the theory that freeway driving will help. At least with a Subaru GDI engine anyways. You'd have to be nuts to go 10k with a Subaru GDI engine. Oil is cheap. Change it more often. Not my engine though....
My Wife commutes to work 1 hour each way at Interstate highway speeds ( for 2/3rds of that) 5 days a week.

I grabbed an oil sample a little bit late in the drain, but I should have results in a month for OCI #1
on a 2023 crosstrek with a 6mt that revs about 3350 on the highway due to low gearing (!)
Just a Black Stoned UOA, but I had the bottle so thought might was well. The drained oil looked not terrible at about 5600 miles on it but the engine is really noisy now when fully warmed and is now running with poor cyl balance vs. how it ran the fist 5K miles. IDK. May just be part of wear in.

The car info is in my signature line below vvv
 
My Wife commutes to work 1 hour each way at Interstate highway speeds ( for 2/3rds of that) 5 days a week.

I grabbed an oil sample a little bit late in the drain, but I should have results in a month for OCI #1
on a 2023 crosstrek with a 6mt that revs about 3350 on the highway due to low gearing (!)
Just a Black Stoned UOA, but I had the bottle so thought might was well. The drained oil looked not terrible at about 5600 miles on it but the engine is really noisy now when fully warmed and is now running with poor cyl balance vs. how it ran the fist 5K miles. IDK. May just be part of wear in.

The car info is in my signature line below vvv
Is that UOA on here?
 
Bout normal fuel dilution for a fuel diluting Subaru GDI engine. I see around 4% fuel in my '22 Crosstrek at 3,000 mi. For that reason and for piece of mind, I do 3000 mi OCIs with this vehicle.😎

I'm doing 3 month/3K OCI's, whichever come first, in both of our GDI vehicles. My '21 Crosstrek gets used for a 20 minute/13 mile drive to and from work three times a week. Last oil change at three months was at 2,200 miles.

The other vehicle is a '21 Acadia Denali. She drives it to and from work 5 days a week. 3 miles and 7 minutes one way. She also comes home for lunch......so lots of 3 mile trips per week....20 of them to be exact.
 
Is that UOA on here?
No I just did the OCI a couple days ago. Might have the UOA results in a month. It was from the first dealer OCI I think they used Valvoline bulk synthetic and the U.S.A Subaru service part "Blue Painted Fram" oil filter.

I was going to use the excellent Genuine Subaru (Idemitsu) oil and the Subaru filter but I went with premium autoparts stuff.
Valvoline Advanced 0W20 and a WIX XP.
- Ken
 
No I just did the OCI a couple days ago. Might have the UOA results in a month. It was from the first dealer OCI I think they used Valvoline bulk synthetic and the U.S.A Subaru service part "Blue Painted Fram" oil filter.

I was going to use the excellent Genuine Subaru (Idemitsu) oil and the Subaru filter but I went with premium autoparts stuff.
Valvoline Advanced 0W20 and a WIX XP.
- Ken
Isn't the Wix XP one of the least efficient oil filters?😳 Possibly worse than the reusable K&P oil filter I'm running. Gonna do a particle count with next UOA to see how bad it really is and then run Fram Ultra for same OCI and do a UOA and particle count with it as well. Curious to see how it pans out though pretty sure the Fram will prevail.
 
Doubtful... My Subaru sits in a heated garage when not in use and I still see plenty of fuel dilution.
Our Subaru is kept in a heated garage. It's exposed to the cold weather during the day at work. I can't imagine how much dilution if it wasn't garage kept.
 
If you are going to keep those driving habits, substitute 1 or 2 qts of 5W30 AMSOIL Signature with the 0W20.

The fuel dilution on DI engine is NOT a good thing. Subaru have narrow bearings, they need more MOFT than a diluted 20 grade will ever provide.

Owned nine Subaru over the years. I have a couple relatively new "clankers in the driveway due to the D.I. "curse" - Ken
Looking at this report the oil viscosity is till within effect. Hardly effected at all with amsoil signature.
 
Looking at this report the oil viscosity is till within effect. Hardly effected at all with amsoil signature.
Fuel dilution has a physical effect on viscosity here, it is a simple dilution based on grade. It’s not dependent on brand.

The only way to counteract fuel dilution with the oil is by grade.
 
Last edited:
Very good feedback on this thread. It's nice to start seeing more reports on newer D.I 2.5L boxer engines. I downgraded and placed an order for Amsoil OE 0W-20. Planning on just changing oil every 3-3.5k miles Spring/ Fall schedule. My next UOA I'll be using a Amsoil filter already on hand. However, after that continuing with standard Wix filters. This should be adequate since the vehicles only driven 6-7k miles annually.
 
Very good feedback on this thread. It's nice to start seeing more reports on newer D.I 2.5L boxer engines. I downgraded and placed an order for Amsoil OE 0W-20. Planning on just changing oil every 3-3.5k miles Spring/ Fall schedule. My next UOA I'll be using a Amsoil filter already on hand. However, after that continuing with standard Wix filters. This should be adequate since the vehicles only driven 6-7k miles annually.
Smart move. Yeah seems like the Subaru GDIs are some of the most fuel diluting engines out there unfortunately. Keeping the OCIs close to 3000mi will definitely help mitigate things more than the "spirited driving on the highway" recommendation. Did not do anything for me to help with fuel dilution.
 
Last edited:
Isn't the Wix XP one of the least efficient oil filters?😳 Possibly worse than the reusable K&P oil filter I'm running. Gonna do a particle count with next UOA to see how bad it really is and then run Fram Ultra for same OCI and do a UOA and particle count with it as well. Curious to see how it pans out though pretty sure the Fram will prevail.
Yes that's what I want if running a hampster-sized filter in the Winter - seeing I cant get a good non-ecore Champ labs.

Last Fram XG I ran on a Subaru MELTED its base gasket to the mounting boss. Hard a very hard time getting it off. Turned me off.
 
Top