Time to switch oils in 2007 Subaru EJ25 turbo with 150k?

[Impatient]

Because the outcome is unpredictable. Add pack compatibility and results and final v@40 and V@100.

If someone were going to mix, I believe mixing Castrol Euro 0w30 with Castrol Euro 0w40 is the most copacetic mix possible. I have no proof, no Tribologist insight, but they really are “kissing cousins.” Also without proof or inside information, I believe the 0w30 is plenty thick for my application, has the 3.5 HTHS, and appears to be recognized as marginally superior (if you like PAO) to the “slightly too thick“ 0w40.

assuming I do a UOA of the mix, I am more concerned with the residual old leftover conventional Valvoline I ran through it for 0-1 mile to test for leaks after replacing an oil cooler o-ring.

 

[Impatient]

I added 100k on a modified car, with the same engine as the OP, with an unpredictable outcome mixed oil.

KV@100 didn't matter to me since I knew it was thicker than the "preferred" grade and KV@40 didn't matter since straight 10W-x could be used down to -4º F.

I appreciate you chiming in, gives me a bit of a comfort feeling and perspective about EJ25x’s.

 

[Vermess]

@Impatient

I've ran 0/5-40 Euro Castrol and Mobil1 in my Subaru vehicles from Temps of -57 to 100+ . Both turbo and non turbo.

Any Euro 0-5/40 available on the shelf at Walmart, buy it, pour it in. No need to over think stuff with a ej.

 

[SubieRubyRoo]

What about the upwards of 20 percent residual oil that was still in the engine? How the engine shears the oil? I am curious on the prediction angle. Are you an oil analyst?

Whether he’s an oil analyst or not is moot. Over the years, we’ve had chemistry masters, oil blenders, and even SOPUS reps give this board scientific reasons to not mix even different oils from the same manufacturer, let alone different grades from different mfrs.

Does it work? Most times. Does it increase your risk for unforeseen issues like ka9mnx mentioned? Yes. As mentioned, different DI packages can have components that “fight” for closest proximity to metals and can have long-term detrimental effects because neither oil is doing the full job it was designed to do.

IMO with what I’ve learned over the years, mixing oils kinda falls into the same discussion/recommendations that oil additives do. If you really think you need to mix oils/add additives/play garage chemist, you probably should just buy a better oil.

And it usually turns out that the more appropriate oil for your needs is actually CHEAPER than the mystery concoction you've whipped up and have no idea what it will do in your engine.

 

[Impatient]

UOA of the (roughly) 50-50% mix of Castrol 0w30 and 0w40. I will ask them to do a GC fuel dilution test, like I specifically asked for originally. Oil Analysers comments are crap, but I like that they do nitration, oxidation, and usually do GC fuel. But I don’t think they did the GC fuel this time, possibly because visc was “up to snuff” (sounds like Blackstone in a way), but they show the oil as 0w30, ignoring my comments it was a mix so “virgin visc“ was higher. It did lose a little visc: down to 11.9 .

Spoiler alert, single digit wear metals again (dang!!!), no surprises. No failure or real anomaly vs straight 0w-30. I will have to explain the Sodium anomaly from the previous UOA which I did not upload at the time. (I think I know why that happened). Prior to previous interval, I replaced an oil filter/oil cooler sleeve o-ring, and did a “test“ fill to check for leaks, the test fill was a very old Valvoline conventional; drained and refilled with Castrol Euro again after the test (I don’t remember if that was straight 0w30 or a mix 30 with 40). After getting the shocking UOA result, I researched and found some evidence old Valvoline of SM (?) vintage was very high in Sodium. I’m hoping that was the cause. Wish pb were zero, but hasn’t been for quite some time. 2ppm ain’t a catastrophe though.

but why in the Hades can’t OA get it through their heads that Castrol Edge includes Titanium, and it’s not a wear metal.

dang I wish my Ford Ecoboost had similar results. At 1/2 the mileage, the Ecoboost UOA results absolutely suck compared to the Subaru’s.

I guess I should somehow transition this to the UOA section.