Fresh Built STi motor - oil type, switch to synth?

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I have a freshly built STi motor that I am breaking in now, using the engine builder's driving recommendations and the recommended Motul 10w40 Break-In Oil (changed after 20 minutes of idle, changed after 250 miles, now on the current oil to complete break-in.
The engine builder recommends a 100-200 mile break in for race motors and a 1500 mile break in for daily driven motors. After that, it says that break-in is complete.

Engine builder's suggested oil is a "high quality synthetic 5w40 oil such as Motul 8100 for street cars or a 15w50 such as Motul 300V for motorsport use."

My question: when do I switch from conventional oil to synthetic oil? I have read here and elsewhere both sides to this and the more you read about oil-related topics, the less you feel like you know when you are done. Is there any conclusive evidence on why or why not to switch to synthetic early? I haven't actually seen that justified with evidence or at least hard data.

I currently have 800 miles on the car and am working on racking the miles up as quickly as I can because I have a tune scheduled for 9 days from now. I will get over 1000 miles for sure by that time but I'm not sure if I'll get to 1500 miles before then. I'm trying to decide if I should just tune on the Motul break-in oil, switch to another 5w40 conventional oil like Castrol GTX, or just switch to synthetic before the tune even if its at 1100 or 1200 miles and not worry about it.

Car is driven in south Florida with a temp range of about 45 degrees during winter nights up to 100 degrees during summer days. Mostly street miles with a few road racing days mixed in each year. Bearing clearances are a hair looser than factory and car should make about 380 whp on 93 octane and about 440 whp on E85.

Also as far as a 5w40 synthetic oil (or even a bit heavier), what do you prefer for a turbo 4 cylinder that is a mix of boring and spirited driving in a hot climate?
On the Motul 10w40 break in oil my hot idle oil pressure is around 22-24 psi now which is good, just not sure if it will dip lower when I start driving the car a bit harder. Oil pressure is around 70-80 psi at 3k to 4k rpm, also good.
 
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+3. Listen to the builder
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I have been defaulting to following the engine builder's recommendations which I agree with being the right move, he just didn't directly outline when to switch to synthetic. I guess it is implied that he meant to do that at the 1500 mile mark, so unless anyone is jumping up and down about why not to do that, it is what I will do.

Also, he left the option of using a different "high quality 5w40 synthetic" oil which is why I was curious there as well. I have heard mostly good, and some bad, about Rotella... I'll have to read more.

I also will keep an eye on my oil pressure to make sure that 5w40 seems like the best weight for my use and environment.
 
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Originally Posted By: FordCapriDriver
Listen to your builder, if anything goes wrong it will be his fault!

Haha... that's optimistic. In the world of built motors, there is no warranty, unfortunately. Hoping this motor treats me well for quite a few miles though
smile.gif
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What are you clearances? Piston type and piston makers clearance recs?

Is this all stock Fuji parts? Stock Sti use 30 grade oil? don't over think or overchange the oil. The break in oil round 3 should be good.

UNCLE_100% (questionable) ADVICE:
Tell the tuner not to go "pig rich" to cover possible boost detonation issues. Tailor boost for only moderate enrichment.
250- 300Hp is all the power that motor should be making safely.

Are you running a whip-it kit on top of the turbo too?
 
Originally Posted By: ARCOgraphite
What are you clearances? Piston type and piston makers clearance recs?

Is this all stock Fuji parts? Stock Sti use 30 grade oil? don't over think or overchange the oil. The break in oil round 3 should be good.

UNCLE_100% (questionable) ADVICE:
Tell the tuner not to go "pig rich" to cover possible boost detonation issues. Tailor boost for only moderate enrichment.
250- 300Hp is all the power that motor should be making safely.

Are you running a whip-it kit on top of the turbo too?


Not sure if I'm muddying the waters here, but if you were serious about your clearance questions:

PTW clearances are .0030 on Cosworth pistons which are made from a proprietary alloy more similar to 4032 alloy with less thermal expansion than commonly used 2681 alloy. Ring gaps are .0017 and .0022.

Main bearing clearances are .0021-.0022, rod bearing clearances are .0018-.0019.

I have a good friend who is a very knowledgeable builder at another shop who said with those clearances, he'd consider a heavier weight oil even with daily driving IF my oil pressure dips below 20 psi at idle. Seems like sound advice, and I plan to start with the Motul 8100 X-cess 5w40 synthetic to see how it goes. Adjustments can be made if needed.

With the Cosworth pistons and Manley H-Beam rods, this motor is rated by the builder to 500 whp, and others have made over that for quite a while. My goals are to stay under 450 whp and be able to enjoy driving the car on the street and road course without issue for a good number of years/miles. Thats the hope at least. I will be running E85 and probably somewhere around 26 lbs of boost to reach 420-440 whp.
 
Originally Posted By: TROLL
My question: when do I switch from conventional oil to synthetic oil? I have read here and elsewhere both sides to this and the more you read about oil-related topics, the less you feel like you know when you are done. Is there any conclusive evidence on why or why not to switch to synthetic early? I haven't actually seen that justified with evidence or at least hard data.


I would not worry about it, listen to the builder, and switch to synthetic.

Even if someone on the internet said otherwise, would you listen to them over the engine builder?

5W40 also doesn't come in conventional.
 
To me it sounds like you can switch to synthetic at 1,500 miles since break-in will be complete. Motul X-Cess is good stuff. Check out this 9k mile uoa from a Stage IV 2.0L WRX:

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2992480

When you compare oils and oil pressure, be sure to look at the HTHS of the oil since that has an impact on oil pressure. Motul X-cess 5W-40 has an HTHS of 3.7 while the Motul 5W40 300V has an HTHS of 4.1. So you will likely have higher pressure with the 300V.
 
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Based on recommendation of builder at 1500 miles I would switch to a quality synthetic with HT/HS minimum of 3.7 as opposed to an actual grade. RT6 would be a good budget choice at 3.7. Motul 8100 is good stuff but spendy. Redline you might want to drop down to 5W30 due to its 3.7 HT/HS as the 5W40 Euro at 4.3 is going to act heavier in the bearings.
 
Thanks for the responses. I am working hard at putting miles on the motor. I drove 80 miles round trip last night to pick something up that I could have gotten free shipping on
laugh.gif
. I'm up to 950 miles now and have at least 200 miles planned for this weekend. My tune is one week from today... I don't know if I'll ALL the way to 1500 miles by the night before when I change my oil but I should get pretty [censored] close if I keep this up.

I'll be sticking with the Motul 10w40 break in until that point and then will switch directly to the Motul 8100 5w40 X-cess synthetic. Thanks for removing any doubt about that here. I found it for $38 shipped for 5Q so its not too bad, I'm ok with paying that. I will probably try to change every 5k miles but we will see how much racing I'm doing.

I still have a couple Purolator PureOne filters left that I'll use and after that I may do some more research there on what is best, but Wix was recommended an engine builder I'm friendly with.
 
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Originally Posted By: TROLL
Thanks for the responses. I am working hard at putting miles on the motor. I drove 80 miles round trip last night to pick something up that I could have gotten free shipping on
laugh.gif
. I'm up to 950 miles now and have at least 200 miles planned for this weekend. My tune is one week from today... I don't know if I'll ALL the way to 1500 miles by the night before when I change my oil but I should get pretty [censored] close if I keep this up.

I'll be sticking with the Motul 10w40 break in until that point and then will switch directly to the Motul 8100 5w40 Xceed synthetic. Thanks for removing any doubt about that here. I found it for $38 shipped for 5Q so its not too bad, I'm ok with paying that. I will probably try to change every 5k miles but we will see how much racing I'm doing.

I still have a couple Purolator PureOne filters left that I'll use and after that I may do some more research there on what is best, but Wix was recommended an engine builder I'm friendly with.


If you want to put some of the best synthetic oil in your STI, I would check out Driven DT40. It is a 5W-40 full synthetic mPAO oil. It was designed for the older water-cooled Porsche engines by Flat6Innovations, and is probably one of the best out there (although it's $10 per quart).

As for filters, check out the WIX XP line. Full synthetic wire-backed media. About $10 per filter. Not bad. I know Subarus have a higher bypass valve spring pressure than just about any other OEM, but for a performance engine, this is a good thing. You want oil to bypass the filter at higher RPMs.

Check out the Wix 51356XP or 57356XP (same filter from what I can tell). They are larger (1" taller, same OD) than the standard Subaru filter, with a 8-11 PSI bypass spring. For the Subaru-spec (size and bypass PSI) filter, it is WIX 57712XP.

Edit: This is an excellent resource for looking up non OEM sized filters. Subaru thread size is 20mmx1.5. You can cross-reference the part number to any other brand once you find the dimensions you would like, if you prefer a brand other than WIX.
http://www.wixfilters.com/lookup/FilterBySize.aspx
 
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Thank you for the recommendations, much appreciated.
As it turns out, my aftermarket exhaust manifold hugs the oil filter fairly closely so I'd need to check the clearance before going to a larger filter, but I will look into that possibility.
 
Originally Posted By: TROLL
Thank you for the recommendations, much appreciated.
As it turns out, my aftermarket exhaust manifold hugs the oil filter fairly closely so I'd need to check the clearance before going to a larger filter, but I will look into that possibility.


You bet. Sounds like a fun car. I can't wait to get my project up and running (1JZ-swapped E46).
 
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