Quote:
Originally Posted by basjoos
You get better mileage at higher elevations because the thinner air reduces the amount of air drag on the car and also because the engine's throttle has to open more (for reduced pumping losses) to produce the same horsepower. Its very similar to the effect that higher outside air temps have on mileage. There's a term called "density altitude" that pilots use to calculate the effect that the combination of altitude and temperature has on the performance of their aircraft.
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I think that must be going on here too, less aero drag especially at speed. But there are balancing factors:
- more dense air at sea level produces more engine power - but then is that power being utilised or wasted
- cooler operating temperatures generally mean less subtle tyre sidewall give with subsequently higher rolling resistance - but then are temperatures simply sufficient anyway.