No. This is definitely not true! Driving a new engine at a static rev range for prolonged periods is not good for the run-in procedure. The whole idea of running a motor in is that revs need to rise and fall, to smooth out any manufacturing kinks on the internal components. That's why you usually find quite a bit of metal shavings on your first oil change. Static RPM = static temperature = bad. The motor (and other components like the gearbox) needs to warm up and cool down a few times so expansion and contraction can take place.
You're more than welcome to disagree, but as far as I know, this is what run-in actually means.
You bet I'll disagree.
A long run is ideal for running a car in, your speed is NOT static at all - varying road conditions will result in all sorts of speeds and conditions. Yes, you will spend long spells in top gear, but that will not affect the box at all.
Your comment about iron filings was certainly true about engines built prior to about 1980, to the extent that some cars (BMC) had a magnet on their oil plug to suck up the filings. This is the 21st Century now, and that is no longer the case.
Static rpm doesn't even vaguely come into it, as variations in road see to the revs changing very frequently - and where on earth did you get that there was a problem with a static temperature?? Why do you think that cars have thermostats? The quicker an engine gets to operating temperature AND STAYS there, the better. You possibly read about the million km Polo last week - that car has lasted so long, PRECISELY because of long runs its entire life.
Expansion and contraction will certainly take place with temperature variation, but it is at that time that the engine undergoes its worst period of wear. Case in point "The little old lady's car" which is historically one of the worst buys you can make, second hand. That engine has done nothing but go through periods of expansion and contraction all its life, and has suffered as a result.
Sorry to burst your bubble, but you are totally incorrect, oh, and please, if you don't believe me, please run your "argument" past the technical department at Subaru, and they will underline what I say about Subaru engines. We have been "running in" their media cars for them for years, and you know how we do it? With long, long runs for at least 2000 km.
