Why does lowering the speed limit on the highway lower your fuel consumption?
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Do you run or bike by any chance? It would make it easier to explain.
When speed doubles, aerodynamic drag quadruples. Make cars go a little slower and their engines consume less fuel per traveled unit of distance.
air resistance exponentially increases as you increase your speed. so cars that go faster have a lower mpg than cars that go slower. the sweet spot for most cars is around 55mph.
its mostly wind resistance, aka drag. that’s after the oil embargo of the 70s cars were designed to be like jelly beans.
I remember reading about making cars (and vans like I had) more efficient. Trucks and vans used to have these big elephant ears, and car side mirros were like flat disks but putting them in bullet shaped domes saved nearly 10% gas consumption. getting rid of radio antennae and for gawd’s sake don’t fly a flag.
then they tucked the whippers under the hood
air dam under the front bumper.
racing cars will tail gate, the 2nd car gets the advantage because the front car breaks the wall of air, it rides in a lower pressure area, and oddly the front car gets an advantage too as the 2nd car redirects the whirlpool of air that would follow it and pulling it back. this method is called drafting.
anyway, cars are, for the most part, designed to move efficiently at 65 now….of course now most folks have higher profile SUVs
It doesn’t always. If you lower from 80 to 60, you eliminate a large amount of aerodynamic drag, and thus fuel consumption, for probably all cars. But if you go from say 60-50, you might increase fuel consumption since cars may not be operating at their most efficient speed, which is usually somewhere between 50-60. This number has been creeping up over the years as cars have become much more aerodynamic.
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