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| quote: | Originally posted by malek
yeah, but they're so minor that its bullshit.
ook at my engine's rev, I see for 100kmh @ ~2000rpm and 120kmh @ ~2400rpm. Looks like my engine is working 20% harder, but also drives 20% faster so it equals itself. But I agree that it varies greatly from car to car (4v vs 6v vs 8v).
And try to explain this, with a full tank i drive around for 400km half highway, half city. And when I do Mtl-TO (550km), I use a full tank driving at 150-160kmh with full ac the whole time.
If infact driving faster used that much more gaz plus AC use, then I would've barely gotten 400km out a full tank even though its only a highway drive. |
Ok, actually it is true that you'll get worse mileage at very high speeds, but the "drag" explanation is completely wrong. You'll also get worse mileage at very *low* speeds.
Take this from an electrical engineer who took two courses in motors and machines: electrical motors are optimized for energy efficiency at a certain RPM. I'm not even talking about the actual efficiency when you take into account things like drag and stuff, but the actual theoretical efficiency of a motor peaks at a certain RPM or current, and for most newish cars that translates to somewhere between 100 - 120 km/h. That's not a coincidence - it's done on purpose, because the manufacturers of those motors expect them to be running at that RPM most often!
So Malek, the explanation you're looking for is: you're losing efficiency when you're driving 160 on the highway, but you are losing a lot MORE efficiency when you're driving 30-60 in the city! "Stop-and-go" traffic is the worst (and there's plenty of that in Montreal!  ), because braking is negative efficiency and accelerating from 0 is extremely low efficiency. That is by far where you waste the most fuel.
Bottom line is, you will get poorer mileage if you go 160 compared to 120 on the highway, but that is still good compared to what you'll get going 40 in the city. That's why all cars have different "highway" and "city" mileage ratings - they are based on the average speed which the car is expected to be moving at under those conditions.
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