I use castrol synthetic 10w40 for my greddy kit in my ap1.

Is that oil fine for the Mase kit with 5857bb? Or 10w30?

Who uses what with their precision bb turbo?

 

thats a debate over suspected bearing wear(more wear requires a thicker oil) and heat tolerance/thermal breakdown(which synthetic helps take care of). people have their preferences, i think your choice will work fine for you.

 

i'm gonna use 5w40 mobile 1 syn for mine.

 

If you use Mobil 1 I would ONLY run the European blend 0W40. It is the only one Mobil 1 makes that still has the ZDDP in it. I run this oil currently.

Besides this one type of Mobil 1, I would run Redline, Motul or Amsoil.

 

i'll use castrol synthetic 10w40. no problems with it.

what would be different if i used 10w30? is it thinner?

 

Yes, it's obviously thinner.
I would at least use a multi 40 weight in FI applications.

 

I use Castrol Syntec 10w30 in winter, 10w40 in summer

 

Its cheap insurance to run one of the better oils I listed. They DO have the anti wear additive ZDDP which is VERY important!