Quote:
Originally Posted by Capt Spaulding
My issue with your experiment is the use of time as a constant. The engine run at 4000 for a month would have turned twice as many revolutions as the one running at 2000. It is not the time that wears the engine nor is it the speed at which the engine operates. It is the number of revolutions the engine turns that is causing the wear. If you want to impose a constant, use number of revolutions. Run the 4k engine half as long as the 2k engine.
At 2k the engine will turn 2880000 revolutions in 24 hours. At 4k it will turn 5760000 revolutions. Which do you think would show more wear? Would it be due the higher engine speed or the greater number of turns. My bet is on turns. To make your example work you'd need to run the 4k engine 12 hours and it too would turn 2880000 times. Then measure the wear differences. Those differences will (or may) be due to the speed of the engine. I'd wager you couldn't measure them.
Or if you wanted to get statistically fancy you could do whatever you want but measure everything precisely and run the collected data through a linear regression routine and identify the relative impact on wear of each of the potential wear factors, holding ALL the others constant. But you REALLY need to compare apples and apples. Your model doesn't.
Your real world example falls victim to the same fallacy. You hold time constant when neither that nor road speed is the important variable. If I run my car in a lower gear, I'm spinning the engine more times. The engine is traveling "farther." More revolutions = more wear. Engine speed may or may not affect wear but you can't determine that until you control for turns. My bet is engine speed is far and away the smaller of the two influences - probably to the point of being inconsequential.
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I don't understand, RPM is just that, revolutions within a specific duration (1 minute).
The topic was cruising at high RPMs. My experiment was related to that. And you just said it yourself:
"If I run my car in a lower gear, I'm spinning the engine more times. The engine is traveling "farther." More revolutions = more wear."
Case closed. When cruising you put less wear on the engine if you do it at a lower RPM/higher gear.
It really doesn't need to be so complicating.
Edit: Also, I agree that an engine running 2K for would have similar wear as an engine running 4K but for half the distance. Actually the one running 4K for half the distance would probably wear less due to extra oiling. But this is hard to apply to the topic at hand, "cruising". Your drive is going to be X number of miles. The goal would be to get there with as few revolutions as possible. Again, it's all negligible. My suggestion to cruise low (not low gear but low RPM) is just a general rule of thumb. No one is going to blow their engine if they don't follow it to death.