Originally Posted by WarmAndSCSI

That's great advice too, but for a factory fresh engine, it doesn't matter. The only thing you have to worry about is the transmission/clutch, be it automatic or manual. The engine should be ready to go from the moment you fire it up for the first time - you only will encounter problems if you're too easy (read: follow the owner's manual procedure) on it for the first few hundred to a thousand miles. That is the biggest mistake people make. Driving it as you would normally = OK. Driving it hard = OK. Driving it too soft = bad. That's as simple as I can put it.

For a rebuilt engine, you get the fastest ring sealing by flogging the **** out of the engine without overheating it for the first 50 miles. You DO have to change your oil after your first idle/leak test or first trip, however. Honestly, this is how many drag racing teams have always broken in their engines - and those last at least a whole season of abuse. This is NOT the advice I'd give to somebody I built an engine for or somebody who bought a crate engine - it's way too risky for somebody who isn't disciplined in breaking in a new engine. I must have done this almost a dozen times now, and I've never had any oil consumption problems except for seal/gasket leaks. I've in fact seen a rebuilt engine never achieve good ring sealing when the owner didn't follow my hard break-in advice. I can almost guarantee the engine would have sealed perfectly if it had been broken in hard.