[chittychittybangbang]

It refers more to how you press the accelerator pedal and a combination of load and RPM. I try to avoid stating RPMs because RPM is not a good indicator of load on the engine. For example, you can rev the engine high in neutral gear and there's no load on the engine. And if you put the car in 5th gear at 20 miles per hour, there's excess load on the engine. Lugging the engine with high load and insufficient RPM is bad for an engine.

So I wrote % throttle/load/power. Here are a few more examples. If you are going downhill in 3rd gear at 40 miles per hour, the engine has little load but higher rpm. This is an example of low % power. But going back up the same hill in 3rd gear at 40 miles per hour, the engine has the same rpm but higher load. Both these situations have different accelerator pedal positions since a different amount of power is requested.

But the overall point of the article is this: a little more or little less during engine break in isn't going to significantly change long term engine health, power, or mileage. All engines have build variation. Don't thrash the engine when it's new and keep rpm and load varying.

Long term engine life depends more on long term maintenance. You can break in an engine fine but if you thrash on it when the engine is still cold, you're going to have more engine wear. I recently talked with someone who said their car's previous owner probably didn't break in the car well, yet their car made more power than most people with the same amount of modifications. Build variation.

I will add some more notes to clarify this in the article.

 

[chittychittybangbang]

Yes, they pretty much say the same thing. A little more or a little less isn't as important as long term maintenance on the long term health of the engine. Letting a 3 year old have a soda won't contribute to obesity but giving them 2 liters of soda every day for life will.

The difference is that I am not so strict about exact RPM for the reasons stated above. RPM is only a partial indicator of what's happening - load is also important and rpm and load depend on the situation. As a general rule during break in, medium rpm with higher load is better than higher rpm with low load since this loads the rings and engine without overloading them.

And automatic transmissions can't control the engine rpm and load as easily as a manual transmission - does this mean that all autos are broken in incorrectly?

 

[chittychittybangbang]

No cruise control. Several WOT runs to 2/3 max RPM then allow it to coast back to lower RPM's is perfect.

I feel no cruise control, varying RPM up and down is important. However, I feel that medium load is better on a fresh engine than WOT at 2/3 RPM. As long as you don't beat on it (most people never beat on their car as long as they own it anyways - how many people take the car to redline more than twice ever? ) on a new car.