I am going to probably hit 3,000 miles on my new engine this weekend and will be changing the oil. I was originally planning on changing over to synthetic at this time, however I'm not sure now.
I have read that synthetic is no good for rebuilds? Would that include a nice tight motor that was bored out and has all new parts, or simply something that was honed/re-ringed?
Also I'm not sure but I think I have a small oil leak at the rear main seal, would it become much worse with the "thinner" synthetic oil?

 

The only time you don't wanna use synthetic is during the time the rings seat and the cam lobes break in a little.

Use synthetic. It's ready.

AJ

 

Unless you installed hard chrome faced compression rings, it's time to commit to syn...

 

last engine i did for myself went 500 miles on 30w pennzoil then went with mobil1 got around 8000 on it now.

 

I just changed over to synthetic at 3000 miles.

 

Myth. Nothing "thinner" about synthetic oil (except at temperatures below the rated temp, like -30 degrees).

Mobil 1 has a reputation for leaking and consuming more than AMSOIL. Otherwise, whether to fix the leak is up to you. Unless installed improperly and it's mechanically getting worse, the leak won't get worse on a fresh engine just because you switched to synthetic.

 

go ahead and run synthetic and you will also get more horsepower not enough to tell though