Best oil for freshly built Subaru WRX STI motor...

[midknight]

I am currently having a 2.5L STI motor put into my wrx. It's the STI 2.5L block with fully forged pistons and rods with the stock crankshaft.

I'm basically gonna have to tune the engine management after the swap is done, at which point I need to drive home ~100miles. My plan of action is going to be to fill the motor with a dino oil for the tune and drive home (which is gonna be the long way so I can avoid the highway) and is gonna involve a few hard pulls to seat the rings. When I get home I'm gonna drain the oil, replace it with dino oil, and then take it easy for the next 3k miles or so.

Does this sound like a reasonable plan?
Which dino oil would be best for break-in? I've been told that oils with more moly are better for break-in but I have no clue which those are or if that's even true... Any advice would be much appreciated. I've sunk a lot of cash into this motor so I want to make sure I do the best possible job breaking it in to ensure a long, healthy life...

 

[Quest]

Castrol GTX, Havoline, Chevron, etc. dinos are good stuff.

I would use 10W40 during the initial phase and change out the oil filter and drain the oil to rid of any abrasives and metal shavings after the first 200miles, and then once again in 1K.

After 2K I'll change out all the oils and then re-access the oil pressure, perform a compression test (wet/dry) to determine the ring seating conditions, etc. before I switch over to using high performance grade oil.

Against most tuner's choice, I often resort to using regular motor oil (dino) during initial phase and not some high EP additive type. So long as the camshaft lobe is properly lubed with assembly lube to begin with, all other parts such as rings (moly vs chrome) and such should seat themselves comfortably. I do not use oil with excessive moly/EP additives for it will slow/interfere the breakin process, esp. the compression and oil rings during breakin phase.

Remember to go easy on the engine during the first 200miles, with 1st 5~10 miles on proper "breakin" period (if dyno is not avail). Making sure you do a bit of engine braking so as to let the vacuum suck lubricant into the much needed ring area to lubricate them properly. You'll be good afterwards.

 

[theguru]

Wouldn't most of the break-in be done on the dino?

 

[Steve S]

you want an oil with the highest amount of additives.

 

[Quest]

I've seen some guys recommending syn oil for freshly rebuilt engine breakin....LOL

Drew99GT is right about the 30~50mph doing it 10~12 times. Chrome rings require more (depending on many other factors also), moly rings take less (abour 3~4 times before they begin to "seat" comfortably).

Make sure you warm up your engine properly (don't let it idle for too long though for if you fix the rpms before properly breaking in the rings/cylinder walls, you may cause some "glazing" effect which is a no-no)

 

[theguru]

I meant dynamometer. After the initial ring break-in, just drive it normally, not necessary to drive it easy. Just don't thrash it. I know this will be difficult to do with an STi.

 

[Drew99GT]

I think I'd use Havoline 5w-30 for this kind of job. Gobs of moly! Someone should chime in with the "relaxed" API rules situation so midknight can tell if the oil he gets is in fact the lower standard stuff or good ol group II. I would definetally do a couple high load pulls to seat the rings. Every repair manual says to do this. "Drive the vehicle to an area with minimum traffic, accelerate from 30 to 50 mph then allow the vehicle to slow to 30 with the throttle closed. Repeat the procedure 10 to 12 times." That is the exact wording from my haynes repair manual about breaking a new engine in. Good luck.