In message , Grimly
Curmudgeon writes
On Sun, 9 Sep 2012 17:57:57 +0100, Bill wrote:

A displacement boat has a "natural" maximum speed (the hull speed)
dependent on the hull length. I've often wondered if something similar
applies to cars in air.

It might explain why in the old Omega, fuel consumption on the motorway
only went skywards over 70, but my current vehicle is bad over 60.

A helluva lot to do with overall gearing and torque characteristics of
the engine, too.

ISTR many years ago someone put forward a figure of 2hp needed to move a
pair of wing mirrors at 70mph.

--
Tim Lamb