Wind resistance goes up by the square of the velocity increase. So as has been noted, speed kills.

So a 20% speed increase from 60 to 72 increases wind drag by 44%! Double your speed and quadruple the resistance, etc. And wind drag is your enemy on the highway when it comes to fuel economy. Weight is the big killer around town.

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2009 VW TDI Jetta Sportwagon 172k miles (rear-ended harder than Elton John on 8/4/13. Total loss)

1991 Volvo 240 142k miles (T-boned by a stop sign runner. Total loss)