i just put rebuilt heads on my evo, so i went with new base gaskets and rings and the whole works. well i was running full synthedic oil , but with the new rings ive heard your supposed to run conventional oil for a thousand miles or so for the break in. well i have a factory case that doesnt have a drain on the bottom to get the oil thats in there out. any ideas?? or can i mix a little syn and conventional? any help thanks, Kodi

 

Don't know the pros and cons of it, or know that's an issue? For years HD was adamant that syn was a no no, however now they don't say that, and if I'm not mistaken their SE models come straight out of the box or at least are set up w/syn, soooooo keep checkin'.

 

Don't worry about it. There's not that much in there to be concerned with and once deluted with dino it won't amount to much. Yes, they will mix just fine. While HD now has Syn3 it is a mix of dino and syn so it will not effect break in much. The fact it has dino in it means it does not stack up to the full syn grades available. It's your engine, so break it in the way you feel comforatable with. I would also go dino initially because I like to dump the oil around 2-300 miles to remove the majority of junk from the first few hours of running. Dino being cheap makes this affordable.

Ron

 

My Royal Purple rep says it's a myth that you cannot break-in an engine with full synthetic, weve did it many times since then and haven't had any problems at all.
They main reason oil companies recommend waiting until after your first oil change is because if your engine is going to have any defects, it'll happen during it's first 3000 or so miles and the manufacture can't point their finger at the oil that you installed.

 

This is from the Amsoil FAQ page.

Q: Are AMSOIL Synthetic Motor Oils and petroleum motor oils compatible?

A: AMSOIL synthetic motor oils are fully compatible with all petroleum motor oils, and there is no danger in mixing the two. Mixing AMSOIL and petroleum oil, however, is not a recommended as a general practice. Performance and long drain intervals will be sacrificed and the oil should be promptly changed, at maximum, within the next 3,000 miles.

 

Almost all motor oils have to meet Military spects. One thing the spects say is thea if you want to sell to the US Military all have to be compatible in their ony usage. Syn oil is good to go for any use, break in or long run. Quiet a few cars and trucks come with Syn oil from the manufactury. I run Syn in every engine and gearbox I own.