Which Oil should I use?

[damojenks]

Hey guys, just been looking more in depth about my engine build and am looking for a bit more info on oils.
Ive just been reading a few web sites, most of them are saying that once my build is done i should NOT use synthetic oils..... Just wondered if this is true????
They said if i use synthetic oils then the piston rings wont sit in right, some old school mechanics say its not true and some say it is....
Im a bit confused as my car has always been run on millers oil, and its what i asked to be put back in. Mechanic said it would be fine but can anyone help me, shed a bit more light on it as i dont want to have to under-go more money spending to get the engine sorted yet again!!
Stress of doing it once is bad enough.... lol ..... Thanks Guys and Girls :hm:

 

[GG205rob]

i think most engine builders would recommend using a mineral oil to run the engine in and then switch to a fully synth before you put too much stress on the engine. This is what i have done when i have rebuilt engines before but they have been lower performance so i don't know if this would be the right procedure for your build aswell.

 

[And@fcm]

millers do a running in oil that you use for < 500 miles and jobs done, I used it in mine and can recommend

 

[micevo]

hi mate i was told by a very well respected engine builder, mineral oil, do 50 miles drain, mineral oil 250miles drain another 250 miles drain then fully synthetic ester based, eg millers, fuch (silkolene),
have a word with your s as all have different running-in process.....

 

[B6lee]

hi mate i was told by a very well respected engine builder, mineral oil, do 50 miles drain, mineral oil 250miles drain another 250 miles drain then fully synthetic ester based, eg millers, fuch (silkolene),
have a word with your s as all have different running-in process.....

Yea I agree with that, that's what I did

 

[Marty.H]

The reason you run a mineral oil is to allow the rings to bed in correctly as a synthetic oil will glaze the bores and they wont bed in.

Also on a fresh build you need to put the engine under load say in like 4th and 5th bring in some boost but DONT rev it to hard the reason you need to load it up is it causes the rings to swell and bed in better. This is how i use to run my race engines in as well as some big powered subaru engines i have built in the past