This discusses low tensions rings of today vs rings from a few years ago.
http://www.drivenracingoil.com/news/dro/training-center/articles/the-chi-of-free-horsepower/Another gibbs article that discusses break in one paragraph
http://www.drivenracingoil.com/news/dro/training-center/articles/dont-fall-for-the-myths/Here is the ol' standby article that gets quoted a lot. It's strange there are a lot of bike engine articles that follow this philosophy
http://www.mototuneusa.com/break_in_secrets.htmSome of the quicker guys I used to hang out with advocated taking the car out as soon as timing was set, and water was up to temperature and make a pass at half throttle, then one at 3/4 throttle, and one more wide open and then the engine was race ready.
That is somewhat analogous to this technique
https://www.flyinmiata.com/tech/breakin.phpMy experience is that after a couple of dyno runs, the power output changes very little on subsequent runs on a properly built engine. Properly built is the key pair of words LOL That means the cylinder walls were properly honed so that the surface does not consist of a bunch of folded over "triangle" tips. In other words, the cylinder walls retain oil but they don't cut the surface off the ring face.
It also means that rings gaps are set appropriately and piston to wall clearance is such that the pistons don't rock more than required in the rings but are not so tight that they expand and force the rings to cut the walls to make their own clearance.
We dump the break in oil out to get rid of any tiny metal bits that are circulating in the system as well as to reduce the chance of plugging up the filter media.
Of course, we all know that we cannot use synthetic oil in a new engine because it is too slick and won't allow the engine to break in (scarcasm) That can only be done on the GM assembly line, Porsche, Mercedes, etc that have magicians assemble their engines and we all know just how much effort they go to to break in engines before we buy the car. (more sarcasm)
In the sixties, Mopar told us to drive the car easily for the first thousand or so miles to insure good engine life and low oil consumption. Actually, I don't know anyone that followed that advice, but, the intent was not to make more power. I don't remember ever having to add oil before a scheduled change.
Today, manufacturing tolerances are more precise, materials are better, and science has evolved. I have heard of a few that claimed their gas mileage got better after a few thousand miles but that is probably hard to prove because we don't have controlled environments to assure apples are apples.
One thing I do know is that it takes a lot less effort to turn a modern engine over with a torque wrench on the stand than it used to and the main component of drag is from the piston rings....as one of those articles mentioned all the rings are lower tension/drag than they used to be even 20 years ago-but if the machine shop screws up the cylinder walls, all is for nothing.
This has nothing to do with break in but it does point out some of the variables involved in ring selection
http://www.dragzine.com/tech-stories/engine-tech-understanding-piston-ring-tension/
