So I just broke in my fresh 460, has maybe 20 miles on it. Do I need to change the oil now or wait a little while?

 

This is one of those questions where it depends....

Usually if you are using hard chrome or chromoly rings, they recommend you allow your engine a proper break in period with regular dino oil before switching or changing.

Theoretically you could change your oil right now just to flush out any rebuilding dirt or metal flashing (shavings) left in the engine. Then refill with dino and then break in for say 1,000 miles or a bit more before a "real" oil change.

If you plan to use synthetic oil this is often more important since some engines will not "seat in" properly if you go to synthetic too soon. If you used synthetic on an engine with chrome rings for example, the rings may never seat in and you may have an oil burning issue forever. So I have read.

The where "it depends" part is if you are rebuilding the engine with modern "factory" style methods and materials. Many factories do put in synthetic as the first oil, but their machining methods etc are usually different than a backyard builder will use or has access to.

If you use a machine shop, ask them what the break in process and oil should be, using your engine components and their machining methods. It all depends.

This is old fashioned and may not apply to you... The way I did/do it is run the engine for say 30 minutes while changing speed up and down a bit. Then I tighten things up as needed. Like, valve adjutsments, head bolts, manifold bolts etc. CHECK THE OIL LEVEL TOO. Then I take it for a good say 100 to 200 mile drive. Take tools, water and oil etc, just incase.

I work my way up to freeway speed at first gently accelerating. Don't let the engine stay at one speed too long, change speeds up and down say between 50 and 70 and in between. Also if you get a nice long hill, let it coast down the hill with no throttle. Even drop it down a gear or two to let the engine do the braking on the hill. After that you can drive the engine normally but not a lot of hard charging until say 1000+ miles. That should do it. OH and check the oil(and other fluids) frequently until your are confident in the engine.

Just my experince from long ago and reading for many years.

Jim Henderson

 

You should have changed it after it ran for 20 minutes. You don't want all the assembly paste, assembly lube, cam break in oil and all the particles that may have came loose here and there in there for long. The oil is basically contaminated after a short break in even if it looks good.