why do some engine maintenance cycles run off hours, like generators, but others off miles, like cars? (Besides the obvious)
In: Engineering
Generators don’t travel. Therefore the only measurement you have to estimate the wear on the engine is time running. Generators also have a constant RPM, whereas cars are variable.
Cars travel, and because they are on the ground we can measure the distance they do. This is a more accurate measure for cars because engine speed is loosely tied to distance traveled. What we really care about in both cases is how many times the crank has turned. Most of the time your car is going to be cruising at 2,000 – 3,000 RPM, so it’s reasonable to extrapolate the number of revolutions based on the distance traveled, with some wiggle room.
Frankly I don’t like either measurement because all that really matters is how many times the engine completed a revolution. That being said, measuring engine revolutions would be counted in the billions over the life of the engine, so I can see why it wasn’t practical before digital sensors became a thing. That does make me wonder, however, if modern cars with oil life meters actually run these calculations instead of using hours or miles. Interesting to think about!
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