"Tim Woodall" wrote in message
e.uk
On Sat, 31 Jul 2010 19:55:31 +0100,
Recliner wrote:
"Tim Woodall" wrote in message
e.uk

Obviously, this breaks down for high performance cars at very high
speeds. I doubt that any road-legal car generates signficant down
force at speeds much below about 100mph due to the dire effect it
has on fuel consumption.

What about the sports cars which have retractable rear spoilers that
pop up at, say, ~75mph?


No idea. But if they do generate appreciable down force then they'll
also cause significant drag and you'll see that in the fuel economy.

Yup, but that's probably not something that owners of cars with
automatic rear spoilers (eg, Porsches) worry about too much.