Question about engine speeds/work

[blue2000s]

Originally Posted by Rail26

I was having a discussion over a couple shots of Don Julio and some chicken mole enchiladas about how hard an engine is working at different speeds. My argument was the following:

Hypothetical: If an engine is turning at 5000 rpms and going 30 mph in first gear or turning 5000 rpms and going 130 in 5th gear...the engine is experiencing the same amount of stress. This was brought about by my buddy saying he would never buy a German car from Germany that was driving routinely on the Autobahn. What do you guys think? I don't think the engine would be anymore less worn out then if you purchased one in the states.

So are you asking if a car is driven for say 50,000 miles at 5000rpm in 3rd gear is better or worse off than one driven for the same miles and rpm in 5th gear? If this is the question, the answer is, it depends.

Engine speed is far from the only thing that effects engine wear. Things like engine load (essentially, how wide open is the throttle), fuel quality, the outside conditions like temperature, humidity, dust content, how well are the oiling and cooling systems maintained, and I'm sure other things that I'm forgetting.

If, instead you're asking if a car that's driven in mostly city miles vs one that's mostly done highway miles, 9 out of 10 times the highway engine is going to be in better shape. Constant changes in engine speed and load and consistant short trips will decrease engine life due to mostly friction and water accumulation.