Switching to conventional to break in after 12K miles?

Hey all. My Legacy GT got an engine rebuild a bit over a year ago and, despite me asking the guy that helped me rebuild my engine to use conventional upon filling the new engine up with oil (this was recommended to me by my tuning shop Surgeline), I'm fairly certain he filled it with the Mobil1 synthetic 5W-30 the shop gets in bulk. My car has seemingly been a bit on and off with oil burning, however it definitely does burn oil. I'm not willing to rule out that my turbo seals are going bad, but the turbo seemed to be in good shape when it was taken off for the engine rebuild. I went through a half quart in the last 1K miles when I checked today which was a little startling considering I, though I maybe got some smiles per gallon on a couple occasions, didn't romp on it really hard for an extended period of time.

 

I'd like to be absolutely certain that the engine sees proper break-in. Should I run some conventional/break-in engine oil when I next do an oil change or is it too late? Does it even matter?

 

Thanks.

I would think that after 12k things are pretty well in place and broken in for the most part. I have heard from a few sources to stay away from Mobile 1, particularly in turbo cars, altogether.

 

It sounds as though it may be worth having the turbo checked out. It woukd suck for things to get worse with such a fresh build. What happened with the heads during the rebuild?

 

Mine needed guides at 71k but that engine didn't consume much Brotella in the 20k I ran it.

 

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1.5 quarts in 3k is high for only 12k on the build unless the rings are gapped for high boost. Still, on my last build I gapped .026 and only burned less than half a quart in 3k after having broken in with Motul 40W mineral oil. That, or valve guides/seals like Whitexc said.

 

I'd have a chat with the builder and get their perspective.

At 12k miles, what's done is done. Have you considered sending an oil sample for testing? Might help zero in on exactly what's going on.

 

FWIW, my wife's '17 Forester burned enough oil to get a low oil warning on the dash screen. We eventually figured out that it was related to the times when she brought it to the dealer for service.

 

Long story short, I encouraged her to bump the viscosity up and the issue went away completely.

 

Something else to consider is how much time the engine has spent idling since new. Extended idling on new engines may result in piston ring chatter which eventually leads to oil consumption.

Send a oil sample off to Blackstone Labs, contact them, they will send you a sample kit.

 

I switched from Castrol GTX to Amsoil 5w-40 European (Full SAPS Classic)at around 3500 miles. Doing 7-8000 mile OCI, after sending a sample off to Blackstone.

 

The engine will begin to use oil after 2000 or so now, some 144,000 miles later. My engine has none of the sounds these engines are known for.

Send a oil sample off to Blackstone Labs, contact them, they will send you a sample kit.

 

I switched from Castrol GTX to Amsoil 5w-40 European (Full SAPS Classic)at around 3500 miles. Doing 7-8000 mile OCI, after sending a sample off to Blackstone.

 

The engine will begin to use oil after 2000 or so now, some 144,000 miles later. My engine has none of the sounds these engines are known for.

 

Max is dead on. I have 5200 miles on my build and went Amsoil from day one. I

am running Amsoil SS 5w-30 now. I will be switching to the 5w-40 Eu on my next change at about 7800 miles as Max is using. I been selling and using Amsoil for so long. So many people use the 5W-40. I have not switched cause my car is now parked inside cause I work from home. takes my a long time to get miles on it.

From playing with Subaru's for well over a decade now, I've learned that Mobile 1 and Subaru engines don't mix well. Mobile 1 seems to thin out like crazy, which isn't a big deal for some engines, but Subaru's don't like it. As Max said, send a sample, but I would also look at 5w-40 or similar, I like the Euro spec oil, but there is a bunch that should work.

I've run Mobil1 5-30 for the last 10 years. No issues.

 

I've never heard of breaking a motor in on synthetic, and then switching to conventional. Isn't it the other way around?

I've run Mobil1 5-30 for the last 10 years. No issues.

 

I've never heard of breaking a motor in on synthetic, and then switching to conventional. Isn't it the other way around?

 

You have a 2001 GT. Not the same beast as our GT's and XT's on oil.

 

Most of us use conventional oil for break in.

 

But what do you think most all new cars come with from the factory...

The oil discussion can be hashed out for decades and has been on other oil specific forums lol.

 

In Turbo Cars prefer Rotella. I am a huge M1 advocate for non-turbo cars as I have run that oil for years without issue. The more specialized oils such as redline are also great oils because of the ZDDP pack additives. But only for racing to track days.

 

Stay AWAY from Royal Purple as it’s just crap.

 

Just stick with the Rotella.

Thanks all. The heads were rebuilt from my old engine with a bunch of GSC parts like valves and springs. The shortblock is a factory EJ257 with 0 miles on it.

 

I've been doing pretty short OCIs forever, around 3K. I'm uncertain if the anti-wear additives in synthetic would prevent any wear from happening over the course of the last 12K miles. I'll speak with my shop and see what they say.

You have a 2001 GT. Not the same beast as our GT's and XT's on oil.

 

Most of us use conventional oil for break in.

 

But what do you think most all new cars come with from the factory...

 

I have a turbo GC that gets the same treatment as the LGT. I use conventional for the break in, and then give it Mobil1 after 1000-1500 miles, and then every 3 after that.

 

maybe this is why all the 4 cylinder chain motors have oil consumption, no such thing as a conventional 0w.

Well, for better or for worse I put conventional O’Reilly’s oil in for this change. Hopefully I’ll see a reduction in oil consumption. If not, gonna assume my turbo seals are going bad, which could definitely be the case.

Well, it’s been just under 1K miles and I’m at, as far as I can tell, no oil burned! Woohoo!

 

I guess this is a lesson for anybody rebuilding their engine: USE CONVENTIONAL OIL! I ran synthetic with 3K mile oil changes for 12K miles on my new short block and was burning a lot more oil than a new engine should be. Just 900 miles on conventional with fairly typical break-in procedures for the first couple days of those 900 miles and I’m back in business.