5w-50 new motor break in

[DGXR]

Synthetic oil is not magical. Compared to conventional (which often has some synthetic content), synthetic oil flows better at very low temperatures and is better at resisting thermal breakdown at very high temperatures (lasts longer). Those are the highlights. Many new engines come from the factory with synthetic oil as the "break in" oil because it does not prevent newly machined parts from wearing in. Also there is a difference between hard driving and abuse. Just don't abuse the engine for the first 500 miles and you're good.

 

[RooflessVW]

So why not use Driven BR?

 

[Astro14]

Spoke with the builder, as I suspected, they basically said synthetic would work, but it's not preferable as it will take the rings longer to seat. Going conventional they recommended keeping the low side and sacrificing the high side during break in as I won't be doing any extended high rev sessions. They said mixing some blends from the same line would be fine, so that's what I'll do, few quarts of 5w-30, few quarts of 10w-40 and a few quarts of 15w-50. They normally recommend a high zinc content oil but said with my cams already worn in it's not as critical.

That sounds reasonable to me. Particularly the part about the cam and the need for zinc.

Broke in a few flat tappet cams years ago with great results, because I used the recommended assembly lube, recommended oil, and then ran the 2,000 RPM for 30 minutes as directed (if that’s right, it was something like that, been a few decades).

I‘m glad you’ve got a workable solution.

 

[AutoMechanic]

I remember seeing some 5W-50 at Rural King you may not have one in your area though. I believe the brand was Amsoil not sure if it was regular or synthetic or like a motorcycle oil or something but I do remember seeing some there.