Originally posted by: Zenmervolt
Originally posted by: 91TTZ
Originally posted by: Smartazz
By driving at 45 rather than 65 mph (72 rather than 105 km/h), wind resistance is about half, and much greater fuel economy can be achieved. Increasing speed to 90 mph (145 km/h) doubles wind resistance again, and further decreases fuel economy.
That sounds misleading. They make it sound like going from 45 mph to 90 mph doubles your wind resistance. That is incorrect.
No it doesn't... It says quite clearly that going from 45 to 90 mph increases drag by 4x.
45 to 65 is a doubling.
65 to 90 is another doubling.
Therefore 45 to 90 is a
quadrupling of drag.
Since speed doubles and drag quadruples, the power requirement increases by a factor of 8 (doubling multiplied by quadrupling means an increase by a factor of 8).
ZV