Higher octane won’t help fuel dilution if that’s what you’re wondering about.Ew
Definitely gonna have to get mine analyzed when I do the Spring oil change in my FA20DIT. I do run 93 octane so I wonder if that's a help.
Two Subarus - common oil? HPL, intervals?
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Dang, I thought my Honda with 4% dilution in 4500 miles was bad. 56ppm copper would have my attention as well as the TBN in the basement at only 3k miles. The Fe at 9ppm in such a short interval isn't that great, but it's certainly the least alarming part of the report.It's certainly good for more power but I don't know that they did anything to address the concerns I'd have as far as oil selection. PCV is still dead simple, and I think the injectors are still junk.
Just got this back.. fairly interesting but expected.
oil was in use from 12-17-24 to 4-12-25 (4 months)
mileage from 11111 to 14273 (3161mi)
Sump capacity 5qt.
>5% fuel in ~3K is not much better. Not sure where the Pennzoil Platinum hype started, but yes, extended OCIs are not where I'd try to save money on a Subaru.
I'm convinced a serial diluter needs some much thicker oil to combat the viscosity loss.
My next OCI, the 15w-40 in my Honda will be getting blended with some 20w-50 (also HPL PCMO; no additive clash).
If this was my car and engine, 0w-40 FS is the *thinnest* oil I would consider...
The only "cure" is high RPM and higher temperature.
The higher rpm helps fuel mixing (higher velocity) and the higher temperature helps cook off the fuel in the oil a bit. But it's only cooking off the lighter fractions-- the heavier hydrocarbons in gasoline will likely take much longer to cook off, and might never evaporate in some cycles.
With winter here, I'm going to be blocking off the intercooler to my car. The cold intake temperatures in most low-load conditions are a huge contributor to fuel dilution, since temperature is the main aid for fuel vaporization.
All the turbo FA24s have an oversized oil cooler, that’s likely where the Cu is coming from as long as it’s not paired with lead or tin.
This. HPL supercar is quite extreme for the 2.5 N/A. WRX/STI? Sure! When I asked Dave about my 2014 outback with the same N/A engine he recommended the vanilla PCMO, which, according to my used oil analysis is doing great and better yet, the price is nice! So you can still get a top shelf oil, extend the intervals safely, and save some bucks over the supercar.Mobil 1 Full Synthetic 0W40 since it's on every WM shelf. If you've turned up the wick on your Rex there's no point in not going to a 40 grade, and EJs have always lived famously on 40 grade.
If you want to spend on HPL, feel free, but SuperCar in an NA EJ may be the zenith of irony, and that's coming from a guy who's owned 5 of them...
And they’re on sale soon!
Oh that’s dangerous! I already have about a 15gal stash, why not add some more?!
5 gal pails, 20% off and $25 shipping… what’s not to love?
It is a thing of beauty! I did that earlier this year. If anyone thinks HPL is expensive they really need to take a look at the 5gal pails on their sales.
Link to UOA
I have also realized after considering the difference in rod bearing size and loading, and oil pump size, between the FA24DIT and FB25 - along with the elephant in the room of DI vs PFI, that I should run different oils in these if I want to optimize each in their use case. So thank you all for helping me get the information that makes it pretty apparent that my idea wasn't the best in engineering terms even if it would be convenient
I have also realized after considering the difference in rod bearing size and loading, and oil pump size, between the FA24DIT and FB25 - along with the elephant in the room of DI vs PFI, that I should run different oils in these if I want to optimize each in their use case. So thank you all for helping me get the information that makes it pretty apparent that my idea wasn't the best in engineering terms even if it would be convenient
I know a guy who run a few rallies a year as part of American Rally Association with his Subaru rally car (I believe it has EJ engine) and he runs that exact oil in it - Mobil 1 Full Synthetic 0W-40.
Honestly, having owned both vehicles, I humbly say you’re really overthinking this. Port-injected FBs will happily run their entire lives on 20 grades, and the FA24, if it were not turbo’d, I’d run a 20 grade in it as well. It’s the turbo, and not even mainly because of the increased BMEP, but because of the turbo itself, that I would run at least a 30 grade. That grade, even with significant fuel dilution thanks to my wife’s driving habits, has returned admirably low wear metals and no signs of distress even at OCIs significantly longer than the average. In a WRX, once you add a couple bolt-ons and a tune, you may need to consider stepping up to a 40 grade depending on what the UOA says the ending viscosity it is.Link to UOA
I have also realized after considering the difference in rod bearing size and loading, and oil pump size, between the FA24DIT and FB25 - along with the elephant in the room of DI vs PFI, that I should run different oils in these if I want to optimize each in their use case. So thank you all for helping me get the information that makes it pretty apparent that my idea wasn't the best in engineering terms even if it would be convenient
HPL PCMO 5w30 took 5% fuel dilution over a 7.1k OCI on an essentially severe service driving style, and everything other than the fuel result and KV100 was perfectly green (viscosity was 8.7, still not even worrisome on something that called for a 0w20 to begin with). That’s pretty darn good in my book for an oil change you can do yourself for cheaper than a Jiffy Lube!
A tribologist told me there is no "CURE". Gasoline in oil permanently and irreversibly changes properties of engine oil.
Hence the quotation marks. There is no real cure. But the worst of it can be somewhat mitigated. You can lower the nominal dilution, but the lighter fractions are all that you remove and it's all but impossible for the heaviest parts of gasoline to cook off because they flash about when oil does.
The final boiling point for gasoline is going to be right around 215C, so it's going to take a LONG time to cook off at more common temps of 100-110C or less.
This is why your tribologist said it's permanent. It basically is because heating oil hot enough and long enough to cook off the last of the gasoline is also going to cook your oil, too.
It can yes. There are really two detrimental effects, the first is the immediate reduction in viscosity which isn't good for anything. Gasoline is not a good lubricant. The second can be long-term degradation to the VII. HPL has talked about this in the past. It makes an undesirable situation more undesirable.
But you're right the oil can't cure the problem, which is an issue with design or some other defect. But you can help to mitigate it.
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What did you end up going with @MDN ?
Also have an FB25 (direct injected) and FA24DIT to maintain. Personally decided on the basic PCMO in 5W-40 as a "close enough" for both with plenty of viscosity overhead for any fuel dilution. Both cars out of warranty, targeting 15k mi/2yr OCIs monitored with used oil analysis to make sure that's smart.
I also bought Euro/Supercar 5W-40 for my BMWs (I do track) but couldn't do the mental gymnastics to justify standardizing all cars on that formula since we have the shelf space for both...
Also have an FB25 (direct injected) and FA24DIT to maintain. Personally decided on the basic PCMO in 5W-40 as a "close enough" for both with plenty of viscosity overhead for any fuel dilution. Both cars out of warranty, targeting 15k mi/2yr OCIs monitored with used oil analysis to make sure that's smart.
I also bought Euro/Supercar 5W-40 for my BMWs (I do track) but couldn't do the mental gymnastics to justify standardizing all cars on that formula since we have the shelf space for both...
5W-30 Euro No VII
Assuming the FB doesn’t end up being an oil drinker I will use UOA to determine how long is best for the interval, probably gather data every 2k starting at 6k. I just took a 3k UOA on the FA and it was good, better than I expected dilution wise, so I will probably try moving to somewhere between 5 and 6k depending on how long I see the HPL retaining viscosity. Or something like this anyway lol
Assuming the FB doesn’t end up being an oil drinker I will use UOA to determine how long is best for the interval, probably gather data every 2k starting at 6k. I just took a 3k UOA on the FA and it was good, better than I expected dilution wise, so I will probably try moving to somewhere between 5 and 6k depending on how long I see the HPL retaining viscosity. Or something like this anyway lol
Nice! Crazy overkill for an FB. I wouldn’t be surprised if you get 15k+ OCI’s on that oil. I’m getting 12k on the vanilla PCMO 5w-30.
What are you optimizing?Link to UOA
I have also realized after considering the difference in rod bearing size and loading, and oil pump size, between the FA24DIT and FB25 - along with the elephant in the room of DI vs PFI, that I should run different oils in these if I want to optimize each in their use case. So thank you all for helping me get the information that makes it pretty apparent that my idea wasn't the best in engineering terms even if it would be convenient
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