• kossa@feddit.org
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    5 days ago

    As I wrote: on long distances it can make a difference. But blasting for 3,5 hours 200 is not safe, so if people do that, they’re endangering themselves and others.

    And obviously different cars use different amounts of fuel to achieve the same feat. But if you took the sports car at 100 only it saves a lot. Power (phys.) is dependent to the third power of 3 of the velocity. It’s just physics. When you double the velocity it’s thus way, way, WAY more fuel than just double the fuel.

    • littleomid@feddit.org
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      5 days ago

      A sports car doesn’t have the same aerodynamics as a family hatchback though. You can’t compare them like this directly.

      • kossa@feddit.org
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        5 days ago

        No, that’s why I didn’t.

        General physics apply to the sports car as well, though. The sports car still uses way, way, way more gas for a higher velocity.

        My point is: gas usage is not proportional with speed. It is factor ^3. People underestimate that.

        So when I cruise on a flat surface at 100kph, I use some 4.7 litres with my car. If I go 120kph, a lot of people would expect an increase of 20%, at max, so roughly 5.6 litres. But it gets to some 6.5 litres, an increase of almost 40%. And if I went 150 or above that shit gets crazy.

        The same applies to the sports car. If people calculate “I drive twice as fast, it’ll cost me twice as much”, that’s a crazy miscalculation.

        • littleomid@feddit.org
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          5 days ago

          Nobody said that though. It’s just not always to the power of three. It can’t be, if you consider aerodynamics and the shape of the car. A pointy rocket doesn’t use the same amount of fuel to go at a certain speed as a G wagon, all other things remaining equal.

          • kossa@feddit.org
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            5 days ago

            It is, see e.g. here

            The sports car has a better drag coefficient and less surface area, that is why at the same speed it needs less power. The “aerodynamics” are factored in only in those coefficients. But the velocity is the dominating part, as it is cubed in that equation.

            But still, I am not comparing a sports car to a station wagon. I compare a sports car to itself at higher velocities. And contrary to popular belief, higher speeds result in an unproportional excess in fuel consumption.