OCI for an oil cooled turbo

[05foresterXT]

I've been a long time lurker on here, but I couldn't find an answer to this by doing a search.

I drive a mildly modified 2005 Subaru Forester XT. By mildly modified, I mean that I have installed a large turbo (TD05-18g) that is advertised as a 400hp (at the crank) turbo. This car is a daily driver, and I like to do a full throttle pull when it's safe to, which isn't very often. Maybe a few times a week, if I'm lucky.

My main concern regarding oil is about change intervals, and the fact that the turbo is an older aftermarket turbo that has no water cooling.

Based on other people's UOAs, and other oil recommendation threads on here, I decided to run Rotella T6 5w40. The part that confuses me is how often do I need to change it? Does UOA tell the whole story as far as the bearing section of my turbo is concerned? I have been running very short OCI's (~3000 miles) because of the oil-only-cooled center section of the turbo. Is there some way of knowing throw oil analysis whether the oil is cooked, and more prone to leaving deposits in the turbo?

According to the Kublin method of determining OCI, I should be changing my oil every 3000 miles, but this is based partly on engine output, of which I don't normally use daily. I have used the calculator on this page:

http://neptune.spacebears.com/cars/stories/interval.html

I usually take it very easy during the last 2 minutes of my drive home, before I shut the engine down. My gut tells me that it should be safe to run this oil to 6000 miles and beyond, but I wonder how I can know that this is safe?

 

[Klutch9]

First of all, I'm jealous... Second, do you have a turbo timer? That'll help cool the turbo bearings down before final shutdown, therefore the oil will not coke up on the bearings. This will extend the life of the oil and your turbo.

 

[SteveSRT8]

I love the timers but they can be problematic in a modern car with all the electronics.

Just be sure and let the car idle with the throttle closed for a few minutes, then shut it down. I used to walk away from my crazy modded Corvair turbo and just let it idle for like 10 minutes, this insures the turbo is at its lowest possible speed and cool when you finally stop the oil.

 

[05foresterXT]

No turbo timer. The turbo timer is in my head, but it can be defeated by the girlfriend. For 90% of my driving, I'm pretty sure that it isn't needed.

I know my car sounds like a lot of fun, but before I swapped the turbo, it was throwing smoke clouds and losing a quart of oil every 200 - 300 miles. Are there any red flags in a UOA that would indicate that it could be leaving coke deposits?

 

[05foresterXT]

Originally Posted By: SteveSRT8
I love the timers but they can be problematic in a modern car with all the electronics.

Just be sure and let the car idle with the throttle closed for a few minutes, then shut it down. I used to walk away from my crazy modded Corvair turbo and just let it idle for like 10 minutes, this insures the turbo is at its lowest possible speed and cool when you finally stop the oil.


So you think that with a proper shutdown procedure, I can run a normal (~6000 mile) OCI?

 

[Klutch9]

Originally Posted By: SteveSRT8
I love the timers but they can be problematic in a modern car with all the electronics.


True. To the OP, do you have an aftermarket or piggyback ECU? Sometimes those have features that make turbo timers very easy to use/install. I personally think that all turbo cars should come with some kind of turbo timer. My father-in-law's 2000 Audi TT AWD had a secondary electric oil pump that would cycle the oil after the car shut down. This way, no gas is wasted because the car doesn't have to keep running, like with a traditional turbo timer.

I would do 5,000 mile OCIs if I were you, and do a UOA if you really want to go longer. Your choice in oil will also serve you well.

 

[05foresterXT]

ECU is stock, but reprogrammed with a custom map.

I have heard stories of people with turbo timers having their cars stolen, so I'm not really interested in installing one, But I'm starting to consider it when it gets hot out again.

Please don't flame me for wasting oil, but last summer, I ran Rotella 15w40 for 2 back to back OCIs that were less than 2000 miles each. I'm pretty sure this was excessive, but I wanted to confirm with the good folks here before I started pushing the OCIs.

So does everyone think that UOA is a reliable means of determining OCI, even with an oil cooled turbo?

 

[Ken2]

Quote:
My gut tells me that it should be safe to run this oil to 6000 miles and beyond, but I wonder how I can know that this is safe?
Change your oil at 3000 miles and send a sample to a testing lab. The lab will tell you both the condition of the oil and the amount of wear metals in the oil. If the report is OK but not great, go 4000, change, and test. If the 3k report is great, change and test at 5000. If that is still good, try for more.

 

[Hollow]

Since the factory OCI from Subaru has been revised to 3750 miles with synthetic, I'd start there and see how the oil holds up for further extension. I'd be hesitant to go past 5k.

Does the new turbo still have the banjo bolt filter? There have been problems with those clogging and oil starving the turbo.

I do think T6 is a good oil to be running though.

 

[SuperDave456]

Originally Posted By: 05foresterXT

So does everyone think that UOA is a reliable means of determining OCI, even with an oil cooled turbo?


I think that a UOA is a really good place to start as a reliable means of determining OCI. That, Common Sense, and comparing your results to others that have similar experiences and you should do alright.

From everything I have read Rotella 5w40 is some robust stuff. It sounds like you don't flog your engine day in and out. I'd start with your standard 5,000 mile OCI and send in a UOA and see how it is.

That's where I would start, but that's just me.

 

[05foresterXT]

Originally Posted By: HollowEyes
Since the factory OCI from Subaru has been revised to 3750 miles with synthetic, I'd start there and see how the oil holds up for further extension. I'd be hesitant to go past 5k.

Does the new turbo still have the banjo bolt filter? There have been problems with those clogging and oil starving the turbo.

I do think T6 is a good oil to be running though.


No screen in the banjo bolt. So no concerns about that thing clogging.

I'll definitely be getting a UOA on my next change at ~3000 - 3750 and post it up on here. Thanks everyone for not flaming me for changing my oil so frequently.

 

[JAG]

Is it a 2.0 L or 2.5 L engine? The former is easier on the oil than the latter. UOAs provide clues about the oil condition and engine wear but they have limitations. Multiple UOAs on the same oil reveal more than a single UOA.

 

[05foresterXT]

Originally Posted By: JAG
Is it a 2.0 L or 2.5 L engine? The former is easier on the oil than the latter. UOAs provide clues about the oil condition and engine wear but they have limitations. Multiple UOAs on the same oil reveal more than a single UOA.


2.5L. Yeah, I plan on running a few UOAs throughout the coming year. Summer and winter are ridiculously different in this thing. The turbo engine really wakes up below 40 degrees.

I'm also open to a more robust oil for the summer, if one exists, and can be gotten locally. I'm not opposed to redline, except that I can't find any place that sells it locally.

 

[aussiek2000]

Don't want to burst your bubble, but you aren't making 400hp. One of my friends in college had a STI spec XT and then some and he made ~325 at the crank, dyno proven. And he Had a lot more done to it than just a turbo.

But to answer your question. Run 3k and get a UOA.

 

[fdcg27]

There have been good UOAs using T6 in Subie turbos and there is also a good recent one using GC.
You might try opening the envelope as you go.
Why not try T6 for 4K and then UOA it just to see how the oil is holding up in use?
You might do the same with GC.
You might be able to go much longer if TBN still looks good, other measured additive levels still seem strong and the oil hasn't sheared too much out of grade.
With a forty, you could shear it down to a thirty and still be within what Subaru recommends.
Remember, it's all about how well the oil holds up in your car as you drive it.

 

[05foresterXT]

Originally Posted By: aussiek2000
Don't want to burst your bubble, but you aren't making 400hp. One of my friends in college had a STI spec XT and then some and he made ~325 at the crank, dyno proven. And he Had a lot more done to it than just a turbo.

But to answer your question. Run 3k and get a UOA.


I've got a lot more than a turbo, and the turbo is bigger than an STI turbo. I'm not here to talk about my modifications. I'm here to talk about motor oils. I have a conservative tune, so I don't think I'm making a full 400 hp, but it's a lot more than a stock STI makes. Please try to keep this constructive.

 

[bluesubie]

Howdy neighbor! I'm just across the Outerbridge off I-287. Yes, as JAG mentioned, uoa's do have limitations. There was no sign of any problems when I blew an OEM turbo with only 20k miles on it. My recent uoa just before it blew showed an uptick in lead to 10 but nothing too extraordinary. I do still have my turbo and AVCS screens and got a P0011 just before it blew. The screens showed no signs of sludge. A Blackstone uoa shows you insolubles, but I dont know how valuable that is in determining sludge or deposits.

What other mods do you have besides the 18G? Is your custom map an open source tune or an AP? Where did you have it tuned? IMO, mods and tune are a huge part in determing OCI.

Nice to see another FXT owner here!

-Dennis

 

[05foresterXT]

Originally Posted By: bluesubie

Howdy neighbor! I'm just across the Outerbridge off I-287. Yes, as JAG mentioned, uoa's do have limitations. There was no sign of any problems when I blew an OEM turbo with only 20k miles on it. My recent uoa just before it blew showed an uptick in lead to 10 but nothing too extraordinary. I do still have my turbo and AVCS screens and got a P0011 just before it blew. The screens showed no signs of sludge. A Blackstone uoa shows you insolubles, but I dont know how valuable that is in determining sludge or deposits.

What other mods do you have besides the 18G? Is your custom map an open source tune or an AP? Where did you have it tuned? IMO, mods and tune are a huge part in determing OCI.

Nice to see another FXT owner here!

-Dennis


It's a pretty standard stage 3 setup. TurboXS TMIC, Cobb uppipe, catless dp, catback, cold air intake, 740cc injectors. I actually am running a Clark Turner tune. It was meant to be a temporary tune until I could get the car on a dyno, but I'm breaking the tires loose in 2nd gear (auto trans) and it runs really smooth as it is, so I'm sticking with it for the time being. I've taken some datalogs, and it isn't knocking or pulling timing. I'm running about 20 psi of boost.

 

[bluesubie]

RT6 is robust oil, but I would definitely do a uoa on a short 2-3k interval to see how much fuel dilution you're getting.
-Dennis