Breaking in a new engine

[Kuripot]

I'm driving a new Hyundai Accent and trying to break it in correctly. The first tank of gas was used primarily around town and when i did take it on the highway I tried to vary my rpms as much as I could. On the second tank I was using it for my 35 mile trip to work every day and haven't been varying the rpms much. What is the concept behind varying rpm and how does that improve the break-in process on an engine? I read where keeping the engine at a constant rpm during break-in can glaze the cylinder walls and keep the rings from seating properly. Is that everybody elses understanding?

The manual suggests keeping rpms between 2000-4000. Sixty mph is at about 3000 rpms and where I like to drive it on the interstate for the best mileage. I guess I should be running it up to 75 mph and back down to 60 occasionally. That's pretty annoying to other drivers for the first 1200 miles. LOL

[GasSavers_RoadWarrior]

Way I understand it is, you have to load both sides of the rings, acceleration at about 3/4 throttle to modest revs, then engine brake it down to a slower speed again, highest gear that has you at legal speeds. Doing that 30-40 times is meant to be optimal with modern ring packages, before changing oil then settling into steady speed light throttle useage for 2K to glaze them off.

[kamesama980]

if you've gone through a tank already, don't worry about it. it's too late. IIRC 80% of engine break in takes place in the first 50 miles, and it's like 95% by 150. that's ring break in. the 1200 mile take it easy break in is because of lawers. yes, load it down good and hard from medium-low rpm to fairly high rpm (ie, get in high gear and go from 2k to 5k). I used to have a link to a site of a guy that did motorbike engine building (2 and 4 cycle) for like 30 years and developed his own break in regime that dynod 10-15% better hp and mpg than the mild-moderate break ins. overall, just let it warm up then drive it hard the first 200 miles without lugging, redlining, or going a steady speed.

[BumblingB]

I posted a few weeks ago and got mention I wasn't breaking my car in properly. I did say I that I hung in certain MPH range so that may be where that was taken from, we never talked about it much more. It did start quite the discussion about different break-in methods. I've always leaned towards kamesama980's way - did I mention I've owned over 100 cars? Many of which I built the motors for (I come from a car family, auto parts, machine shops, gas stations, body shops, performance shops etc - everyone owns something)

(the thread is here, it was about my new smart)