ace rimmer

got an import (94) wrx sti a few bits and bobs done here and there baisicly witch oil should it run on as everyone has a diff opinion it seems, i have owned the car for 6 monthes ran it on 5w 30 everything was fine then i was told its defo no good for the engine get 15w 40 in to it and the oil book in halfords also said 15w 40 so i put it in on saterday and buy sat night it it seemed to be smoother and alot lighter on fuel from the get go and on sunday night it holed a piston i know a bit about engines and cant see how oil can make this differ but i'm convinced it was, so new block there with my old heads on it all built up ready to be put in tommorow so what oil do i run it on 5w 30? and long to run in the gaskets? 200 miles be plenty p.s before i go its only runing 1 bar of boost and ita always on optimax didnt think this coud be enough to melt pistons one way or another

vulnax999

iTrader: (7)

A good fully synthetic oil ONCE ENGINE is RUN IN, 10-40 is about right I believe - search on here or ask Oilman,


PS Imports need Optimax or similar higher quality fuels and preferably octane booster like NF race or Millers, as they are mapped for 100 octane in Japan. That's probabl;y why it went, in the recent hot weather?



SMAKIBBFB

what a guy!

ace rimmer

once engine has been run in what oil until then and do you think my piston melted because of to much boost or what as i have never herd the car pink at all

Kenny.S

Unless the det was really bad i very much doubt you would hear it, it's most likely to occur when on boost and by this point there is far too much noise being made for you to hear.

I had my 95 Sti Ra checked for det b Andy.F using det cans when i bought it. It was runnin optimax and booster but still managed to det a little up through the gears (the ecu managed to correct this) and quite badly when on full throttle in 5th.
I have since discovered that my car has been chipped in Japan and this is prob compounding the issue.

As for the oil thing it does seem like a strange coinsidence that it failed a mear day after changing to a different grade oil. The only explanation i could suggest is that the lighter oil was able to get in and around the pistons more easily and help keep them cool? This would be on the basis that the engine was detting and was prob on the verge of melting anyway. Could be wrong but thought it was at least worth a mention?

Kenny

ace rimmer

no mate much apreed thanks for everything i think i'll go back to 5w 30 and get a air/fuel gauge though and see were i go from here thanks for all the info though

vulnax999

iTrader: (7)

OK, run in on normal good quality oil, say 10-40, castrol GTX perhaps? Synthetic oil is "too slippy" for running in! I suggest Motul 300v, Mobil 1 motorsport as a start.

AFR gauge is good, I have the Autometer one, its good.

Det would occur when you load up the engine, say full throttle between 4000 - 6000 rpm and on full boost or uphill or loaded with people etc.
A knocklink would flash to warn you of those instances.

Kenny.S

I would be a little wary of using such a light oil, there are people using it without any problems but there are issues with it. The majority seem to go for a 10w40, 10w50, 15w50 or something along those lines, silkolene pro s, motul 300v, millers, shell etc.

When you put your new engine in i would use a good semi-synthetic 10w40 shell helix for example (bit dubious of running in oils, how do you know you've got it all back out?) Do a few hundred miles or so then change the oil and filter. Do another 800+ miles off boost but dont let the engine labour on hills etc Then put in your chosen oil.

I would then get the thing checked for detonation by a good mapper who will be able to advise you of the best way to correct the problem. This may result in a re-map or just running more octane booster but either way it's better that than melting another piston.


Kenny