2019 Subaru Ascent FA24, 7.1k, HPL PCMO 5w30

[SubieRubyRoo]

Welp, after some USPS shenanigans, WearCheck finally received my sample from October 11th on November 7th. Good thing I put it in a Priority flat rate envelope; if I had shipped it ground WearCheck may not have gotten it until Easter 2027!

Anyways, fuel is down and here’s my theory: wife’s daily commute of 14 miles, combined with the serious oil cooler mean even in summertime the oil never gets over maybe 186-187*. So my plan of attack this OCI was that every time I drove it, I would run the CVT manually and maintain ~3k RPM and about 62mph until the oil was 212*+ for at least 15 miles or until I got home. Unfortunately for the last 2-3 weeks of this OCI I was unable to get the oil hot and I think that’s part of the reason fuel was still 4.8%.

Considering iron is just above 1ppm with ~5% fuel and probably 10-12% of this OCI at 3k+ RPM, shows even the “base” @High Performance Lubricants oil is robust. Viscosity is down just a touch, for obvious reasons but since this engine specs a 0w20, there’s still plenty of safety net here.

To my final part: I’m actually considering removing the oil cooler and replacing the two hoses with a single piece so that it just loops around since the cooler is too good at its job. Heck, even on a 850+ mile trip this summer with the trunk full and the Speedo between 75-80mph, the oil was only 205-207*F.

Am I crazy for thinking of removing the oil cooler?

On to the report!

 

[tired]

Thanks for the report. What is the VOA oxidation?

How do you like Wearcheck vs Polaris?

 

[rstsco]

Welp, after some USPS shenanigans, WearCheck finally received my sample from October 11th on November 7th. Good thing I put it in a Priority flat rate envelope; if I had shipped it ground WearCheck may not have gotten it until Easter 2027!

Good to hear it finally made it to its destination and not lying in a ravine close to the mail carrier's house.

Thank you for showing a Wearcheck report. I'm making the switch to them from SpeeDiagnostix and have my latest OCI sample waiting for me to get around to shipping it... via UPS or FedEx. Also going to send in some HPL Premium Plus PCMO for VOA since it's what I'm going to be switching to. Maybe I should now wait until after Christmas.

 

[CarbonToast]

Yes, I think you are crazy if you remove the oil cooler. Why is the temp range you list a bad thing? You dont want to cook the oil. Is there a thermostat ?

If you're so inclined you could block part of the airflow across the cooler with duck tape and cardboard as a test. Do 50% coverage, then 100% and monitor.

 

[himemsys]

What is the VOA oxidation?

We have two VOAs of this oil in the Database. Looks like oxidation starts at ~34.

 

[bluesubie]

I know what you mean about those oil temps, as my daily commute is 6 miles each way, but I still would not remove the oil cooler. Even though I also do it on occasion, I wouldn’t use the flappy paddles regularly to try to get the oil temps up quicker since it uses more fuel. And also because my neighbors would be even more annoyed with my AWE exhaust. I did a trip to Charleston and Savannah from NJ in early October. With ambient temps in the upper 70’s to low 80’s, I don’t think I ever hit higher than 209°.

Having owned Subaru’s since 1997 and turbo Subaru’s since 2002, I think this is Subaru’s best turbo engine. The first few years of the Ascent were the beta testers.

I would suspect that there are many FA24DIT owners that have much higher fuel running bulk 0W-20 and you don’t hear of issues like you did on the EJ turbos. I cringe when I see people complaining that the remote start only runs a maximum of two five minute runs after starting. Imagine their fuel dilution.

You’re running a very robust oil, so I wouldn’t stress about it unless something alarming shows up in addition to the high fuel. Presume that you took the sample when hot?

 

[SubieRubyRoo]

Yes, I think you are crazy if you remove the oil cooler. Why is the temp range you list a bad thing? You dont want to cook the oil. Is there a thermostat ?

If you're so inclined you could block part of the airflow across the cooler with duck tape and cardboard as a test. Do 50% coverage, then 100% and monitor.

It’s not an oil cooler like a plate & fin or tube and fin. It’s a water-to-oil cooler where engine coolant circulates through a small heat exchanger that sandwiches between the engine block and oil filter mount.

The temps well below 200* are “bad” because these engines are known diluters due to the DI, and my test this OCI showed that routinely getting the temps above 212* may have allowed a reduction of what fuel stayed in the crankcase. 212* is also needed to get rid of any condensation from the short-trips. There’s really no downside to getting the temps up.

 

[SubieRubyRoo]

You’re running a very robust oil, so I wouldn’t stress about it unless something alarming shows up in addition to the high fuel. Presume that you took the sample when hot?

Remember, unless I put a concerted effort into pushing this thing *hard*, it doesn’t get above warm in normal use. It was probably 180* but that was like a 6-mile loop around my block one time.

I don’t do the elevated revs early, only when it’s already been at operating temps for awhile and the oil temp has plateaued. Then when I get about 15 miles from home I put it in “fifth” () and set the cruise at 62, and let it percolate. Doesn’t appear to faze the engine at all.

 

[RDY4WAR]

I share your concerns about the oil cooler. My '25 F150 3.5TT rarely sees oil temps over 185°F. This morning, with ~50°F ambient temp, the oil temp was 175-178°F (coolant = 190-195°F) after 40 minutes of 70 mph on the highway. I've considered installing a 200°F in-line thermostat for the oil cooler so that's it's still functional but only when I need it to be.

The report looks great though. The fuel is a little high, but I wouldn't feel concerned.

 

[Hohn]

Warmer oil can be better if the oil has the oxidation resistance to make OCI with those elevated temps.

The concern I have with warmer oil as a countermeasure for fuel dilution is that the fuel evaporates quite unevenly in terms of its constituent hydrocarbons.

In one hour at 100C oil temp, an existing 5% dilution rate will drop to about 0.4%, but this remnent will be almost entirely the c9-c12 components of gasoline as all the lighter fractions evaporate quickly. In local hot spots like pistons, the higher fuel dilution and higher temperature will contribute to piston deposits that the oil must prevent or remove.


I'm becoming convinced that oil dilution in this turbo GDI engines is primarily a low AIR INTAKE TEMP problem. These engines almost all have a charge air cooler on them to reduce knocking tendency. My own Accord will happily maintain intake temps just only 5c above ambient at low load.

That means when you are cruising down the highway at little to no boost and low load, the engine is getting a really cold intake air blast that prevents effective fuel vaporization. I'm going to be blocking off my intercooler (technically charge air cooler since an "intercooler" is between two stages of compression) and trying to raise intake temps closer to 100F.

 

[mt23]

Subie, would you consider using fuel system cleaner regularly for an OCI to see if dilution decreases? Say, Berrymans B12 chemtool as directed every 3rd tank of fuel for continuous use?

I used boroscope camera the other day for a friend's direct injected crosstrek (I know, different engine) and there was carbon all over the injector tip. The engine uses almost no oil, had spotless combustion chamber cleanliness minus the injector tip carbon.

I told my friend to use B12 every 3 tanks and will check camera again

 

[tired]

We have two VOAs of this oil in the Database. Looks like oxidation starts at ~34.

Wow so the oxidation went up about 5 in 7000 miles with fuel dilution. Very impressive.

 

[tired]

Subie, would you consider using fuel system cleaner regularly for an OCI to see if dilution decreases? Say, Berrymans B12 chemtool as directed every 3rd tank of fuel for continuous use?

I used boroscope camera the other day for a friend's direct injected crosstrek (I know, different engine) and there was carbon all over the injector tip. The engine uses almost no oil, had spotless combustion chamber cleanliness minus the injector tip carbon.

I told my friend to use B12 every 3 tanks and will check camera again

I hope I can find where you report back on this. Will be interesting to see if there's cleanup.

I saw a video on Redline SI-1, and the cleanup was very impressive on the carbon at the injector tip on just one bottle. It was scoped before and after. Two bottles (on two tanks) cleaned it up very impressively. I'll see if I can find it. I'm thankful I have two port injected vehicles.



This one shows how quickly the deposits return, but he includes some before and after photos from his Redline runs. I like his videos because they're short and to the point.

 

[SubieRubyRoo]

@mt23, I’m pretty sure there’s no (or as minimal as possible) carbon on the injectors. I use HPL’s fuel system cleaner (was actually in for the first tank of gas on this OCI), and Dave says their stuff has PEA and PIBs and some other stuff that only makes sense to guys like @MolaKule and @Tom NJ. The Ascent has probably averaged one bottle every 8-10k since I got it at 55k miles.

Long story short, HPL says every current beneficial additive they can get their hands on is in the bottle. It’s so potent it must be shipped hazmat, so I just swing by Manteno once a year and buy a whole case.

Thanks for the report. What is the VOA oxidation?

How do you like Wearcheck vs Polaris?

Wearcheck is great. Their phone app is a little weird, but it's great to be able to do everything from your cell. Worst thing is you must take 2 screenshots to capture the report... no way of downloading as a single page.

 

[rstsco]

I saw a video on Redline SI-1, and the cleanup was very impressive on the carbon at the injector tip on just one bottle. It was scoped before and after. Two bottles (on two tanks) cleaned it up very impressively. I'll see if I can find it. I'm thankful I have two port injected vehicles.

Too bad there was no mention of the fuel type and brand used during testing.

 

[tired]

@mt23, I’m pretty sure there’s no (or as minimal as possible) carbon on the injectors. I use HPL’s fuel system cleaner (was actually in for the first tank of gas on this OCI), and Dave says their stuff has PEA and PIBs and some other stuff that only makes sense to guys like @MolaKule and @Tom NJ. The Ascent has probably averaged one bottle every 8-10k since I got it at 55k miles.

Long story short, HPL says every current beneficial additive they can get their hands on is in the bottle. It’s so potent it must be shipped hazmat, so I just swing by Manteno once a year and buy a whole case.


Wearcheck is great. Their phone app is a little weird, but it's great to be able to do everything from your cell. Worst thing is you must take 2 screenshots to capture the report... no way of downloading as a single page.

Thanks. I'm deciding between Polaris and Wearcheck for a used oil analysis.

I wish I could get the fuel injector cleaner from HPL! I don't live close.

 

[tired]

Too bad there was no mention of the fuel type and brand used during testing.

Yeah he's not US-based, so poor quality fuel could be contributing.

 

[scrllock]

Interesting thing to me is that even HPL shears or dilutes to a 20 grade in these engines.

I would not be overly concerned with the oil temps, you get plenty of evaporation even if the average temp isn't 212F+. I wouldn't disconnect a water to oil cooler either, as it also functions to bring the oil up to temp faster.

I don't think you can do much for dilution on these with cleaners. My understanding is the hitachi injector internals are just a poor design or very poor tolerances, talking to guys who rebuild them for a living. Plus that Outback XT UOA that had 5% dilution at 3k on the oil, only 14k on the motor. That's not something you can fix with a cleaner.


Intake air temps certainly make it worse. Everything about driving in winter really. Cold starts (fuel clinging to the cylinder walls is worse), denser air charge, plus people tend to idle more and maybe avoid longer trips, especially if you're uncomfortable with road conditions.

 

[SubieRubyRoo]

Interesting thing to me is that even HPL shears or dilutes to a 20 grade in these engines.

I would not be overly concerned with the oil temps, you get plenty of evaporation even if the average temp isn't 212F+. I wouldn't disconnect a water to oil cooler either, as it also functions to bring the oil up to temp faster.

I don't think you can do much for dilution on these with cleaners. My understanding is the hitachi injector internals are just a poor design or very poor tolerances, talking to guys who rebuild them for a living. Plus that Outback XT UOA that had 5% dilution at 3k on the oil, only 14k on the motor. That's not something you can fix with a cleaner.


Intake air temps certainly make it worse. Everything about driving in winter really. Cold starts (fuel clinging to the cylinder walls is worse), denser air charge, plus people tend to idle more and maybe avoid longer trips, especially if you're uncomfortable with road conditions.

There’s no shear here. It’s pure dilution. The last run was with No VII series and still lost about 0.5cSt, which I could give a flip about since I’m not using a 20 grade.

I’m going to make a point that before the next oil change, I’m going to spend at least 15-20 minutes with the oil 212*F or above and then drain a sample immediately since I’ve got a Stahlbus valve.

I don’t agree with your thoughts on oil temps in the 180s not being a contributor; the last UOA was a summertime sample with just her local trips, so ~15 miles each way, in ambient temps of 75-90*F, and oil temps maxed out between 196-198*F, which returned 7% fuel. This UOA like I said had probably 500 miles at various times where the oil temp was 215+, and it was the lowest fuel result even though there was some extended idling due to early-onset winter here. I liked the idea about the thermal valve, not allowing coolant to flow thru the cooler until the oil is at least 200* or so…. Will have to look into that.

 

[RDY4WAR]

If you remove the 4.8% fuel, the KV100 becomes 10.1 cSt.

When factoring the approximate distillation curve for E10 pump gas, the difference between 180°F oil temp and 220°F oil temp would be +/-0.35% fuel dilution. It shouldn't make much difference.

Regular 87 E10 pump gas

IBP - 95°F
5% - 118°F
10% - 128°F
20% - 139°F
30% - 148°F
40% - 155°F
50% - 198°F
60% - 233°F
70% - 257°F
80% - 282°F
90% - 318°F
95% - 338°F
FBP - 386°F