How important is it to break in a new engine?

Answer

According to Castrol technology centre (Motor Cycle News February 16th 05) you should just ride normally for about 500 miles. Don't ride too gently or thrash it. The worst thing you can do is load the engine at low revs (by changing gear to early) or use very high revs early on. Having said that, the article states that the power difference between a properly run in engine and one that has been thrashed from new is only about 3% which you probably wouldn't even notice.

It is important to follow the procedure in the owners manual as close as you can(within reason)to extend the life and reliabilty of the drivetrain and related parts.One purpose for doing this is to run the through "heatcycles" so that the engine and its internal parts have a chance to expand and contract.Doing so will help metal surfaces that "mate" together(pistons,valve seats,gears.etc)seat or mesh better for proper operation.It also helps gasket surfaces seal together to prevent leaks over time.Some people belive that engine tolerances machined on modern motors prevent the need for this,although people paying to have chronic oil leaks repaired often disagree.

First answer by Phillbaker. Last edit by TheToeCutter. Contributor trust: 21 [recommend contributor]. Question popularity: 79 [recommend question]