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

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DFW, TX
I suppose if I get 20 answers, I’ll get 20 different opinions. But here goes:

2007 Outback XT with stock motor, (but not stock suspension) has had a steady diet of Castrol for 50k+ miles: mostly 0w30 Euro Edge A3B4, but recently a mix of 0w30 and 0w40, which are supposedly quite similar, so I thought extra mixable…given that 0w30 is hard to get, vs 0w40 readily available at Walmart. Now at 150k, and sweating bullets something is about to go. Original head gaskets, and original turbo. More stop & go than highway. But occasional misbehaving. FYI, this engine did not like Pennzoil Platinum, though that was a long time ago (90K ago…first change after buying used at 52k. For 60k-95k mostly used Mobil1 5w30 ( with maybe ~20% 0w40 mixed in, thinking that would be more stout than the straight M1), followed by the last 50k or so of Castrol.

several possibilities, help me choose (or confuse me further):

1) step up to straight Castro Euro Edge 0w40, which will be thickest oil ever used in this engine (vs 50-50% mix 0w30 and 0w40 last 2 fills)
2) pay Amsoil-like pricing for maybe the last remaining case of 0w30 Euro Edge in the area. Could just be me, but I think engine likes this oil.
3) step sideways to Mobil 1 FS Euro 0w40, which again would be thicker like #1.
4) use Amsoil SS 5w30 which I bought for my other vehicle; this would be the thinnest / lowest HTHS oil this engine has seen in a long time…maybe since the Pennzoil @56k. The good news is it’s “free” for now, but I worry about such a thin oil in this “thickie-loving” engine design, plus probably better suited for the Ford EB, and I’d probably choose something equally pricey for the Ford since long summer intervals for it are my preference.

I really did think the Castrol Euro (German then Belgium) 0w30 was ideal with virgin KV100 above 12 and HTHS 3.5 or so, and plenty of PAO, though surely newer oils have improved??? All the chatter about HPL and cleaning has made me question most all my previous thinking, but my UOA’s with the Castrol were dam*d good. I plan to do UOA again this time.
 

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PP 5w30 euro L is pretty thick. 12.5cst?
if you are looking for walmart available good value options.

Rotella 5w40 was traditionally a common well liked oil in those engines.
 
What issue are you trying to solve? I'd just use any old group 3+ synthetic and drive it until it dies. Oil isn't going to affect a head gasket failure. At this point, even if the car died tomorrow, you have more than gotten your moneys out of it. If it does have a mechanical issue, fix it and continue on with your life.
 
It barely gets cold here in texas. But more importantly how much oil does it burn. And what's your trans, t case, and diff service history.

I run 15w-40 and my trucks start fine even with old batteries. Also why so concerned about a euro 30 and 40. Euro 30's are at the very top of the scale to achieve the 3.5hths minimum and are typically 12.5 kv100. And euro 40's are at the bottom and are around 13-14 kv100. I wouldn't worry if i were you and just use whatever euro 0/5w-30/40 you can get at Walmart. No need for anything boutique. QS euro 5w-40 is SP, Bmw ll-01, mb 229.5 and Porsche A40 rated. Pretty good. Only m1 0w-40 and Castrol 5w-40 can match that. As for formulations It's the specs that dictate the performance not so much the contents. A modern low pao oil can be made to outperform an older high pao blend oil in almost everything except super low temp pumpability I wouldn't worry about that unless it gets brutally cold which it doesn't.
 
I would go with the Mobile 1. 150K is nothing in today's world. There are many vehicles out there where the engine is the last thing to go. You already won at 150K but keep on keeping on.
 
What issue are you trying to solve? I'd just use any old group 3+ synthetic and drive it until it dies. Oil isn't going to affect a head gasket failure. At this point, even if the car died tomorrow, you have more than gotten your moneys out of it. If it does have a mechanical issue, fix it and continue on with your life.
Maybe, but motor seems happier with thicker oil. Today’s USA SP 5w30’s are much thinner than this motor is used to. The Pennzoil I ran 90k miles ago had more metallic sound, and even M1 had some. The Castrol, possibly because it is Euro (3.5HTHS), were quietest, smoothest. So if using group3+ SP oil, I would want it to be thicker than 5w30.

”gotten my money’s worth:” maybe so, but I can’t afford an equivalent / better vehicle new. I’m blown away by how much money people spend on their rides…maybe they make a lot of money. I am on social security with a tiny, and I do mean tiny, pension. Mazda CX5 turbos run $45k. Sorry, but that kind of money’s an issue. I barely trust any DI engine, and few cars match the HP, handling, STEERING (zero torque steer)…the Bilstein suspension is a factor too... as is the manual transmission. Admittedly, I wish I got 50% better gas mileage, and on regular vs premium gas, but today’s performance SUV’s or crossovers probably get even worse mileage, and handle like pigs…but open to suggestion. A buddy’s Cherokee turbo Trailhawk (?) is quick enough, has a real transmission, is more comfortable (+++) but steering feel sux, as does general handling. I’m sure it would be MUCH better off-road, but that’s not my use case. Oh, I do like sitting higher in it, I’m tired of seeing the underside of Texas trucks, so many are lifted.
 
I'd use the QS Euro 5w40 which is close to a 30 weight (on the thin side of 40 weights) and available from Walmart for $22.97 for the 5 qt. jug.
Yeah, that’s a thought. Given Euro, it probably has decent HTHS. I tried the USA version 5w30 in my Transit van, and it was shot after less than 3000 miles, but maybe the Euro 5w40 is drastically better. For that matter, Pennzoil Euro 0w40 might be available at Wally’s, and might be an option. Frankly, it’s been getting A3B4 oil for awhile, but maybe that is old-school thinking and leading to deposits, not sure. C3 or mid-lo SAPS oils might be better. I’m not sure if I’m learning things or just getting confused. But I am resistant to ROTM or MOTR USA synthetic 5w30. I push the recommended 3750 mi interval to near 5000 Miles, but that’s still low by today’s standards. Still, the Subaru‘s FE and CU are dramatically lower than my Ford’s.
 
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I would love to see your engine run HPL personally. I would love to see the oil filter cut open, the used oil analysis, and the changes if any to oil consumption. I wouldn't hesitate to use m1 0w40 either like I do in most subarus I service.
 
I would love to see your engine run HPL personally. I would love to see the oil filter cut open, the used oil analysis, and the changes if any to oil consumption. I wouldn't hesitate to use m1 0w40 either like I do in most subarus I service.
I would love to see my Transit run the HPL. this Transit has been running “mostly” Cummins Valvoline Premium Blue Restore 10w30, which has some similarities to HPL. No one talks about this.

I am a bit concerned the HPL “cleaning“ formula could affect the Subaru head gaskets, though I think (Hope) my generation had the “improved” head gaskets, or possibly had them swapped in before I bought it. But it was a Louisiana dentist’s car, and you know dentists never flog their cars 🤣😂🤣

by the way, you mentioned oil consumption: since replacing the oil filter/cooler sleeve O-ring, consumption has gone to “negligible.”
 
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Turbo, hot running engine , small displacement (2.5?), 4-cyl, high rpm , old car with 150K miles, summer time ... I would try a Euro xW-40 since Euro or a3/b4 0W-30's are for some reason too pricey! If it wasn't a turbo, I would drop my Euro requirements.

Now after all this, what does the OM say? lol
 
I am a bit concerned the HPL “cleaning“ formula could affect the Subaru head gaskets, though I think (Hope) my generation had the “improved” head gaskets, or possibly had them swapped in before I bought it. But it was a Louisiana dentist’s car, and you know dentists never flog their cars 🤣😂🤣

by the way, you mentioned oil consumption: since replacing the oil filter/cooler sleeve O-ring, consumption has gone to “negligible.”
The 07 EJ255 head gasket is MLS and not known for external oil leaks. Not saying it's impossible but I think unlikely to develop an external head gasket leak large enough to warrant replacing the head gaskets. Negligible oil consumption for the win 👍
 
By the way, I’m not crawling under the car in 100F temps to change the oil. F that. We sure need a cold front , to lower temps a bit. Weathermen very pessimistic this year. I’m usually up in PAC NW or somewhere else cool for the summer living out of the van. This year, stuck in Texas, doing elder care. speaking of, I’ll have to check back later.
 
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