Engine efficiency itself is only one part of the fuel economy situation.
Rolling resistance, gearing, brake drag and of course aerodynamics paly a
big role. All vehicles suffer fuel economy losses as speed increases.
Vehicles with large front faces and poor aerodynamics really suffer. Here is
a chart that gives the horsepower requirements for different vehicles at
different speeds.

http://www.cat.com/cda/files/2222280/7/LEGT6380.pdf

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
mark drillock
Sent: Saturday, February 04, 2012 8:02 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Slow Down And Save Some Gas

Unfortunately, most cars today are built with far more powerful engines than
cars from that era. It seems that much of the efficiency improvements of
modern engines has been squandered by a drive for ever more power rather
than better and better fuel economy. At least a few modern engines can be
adapted to our Vanagons and of those few the smaller ones can give us better
fuel economy than our stock engines can, at least for those with stock
gasoline engine Vanagons.

Mark

Jim Felder wrote:
> The point was probably to reduce, but not necessarily to optimize.
> There are vehicles out there that might reach maximum efficiency at
> 45. All vehicles may do better at 45 than 55, or they may not. I think
> they just picked a number that would save fuel and people could more
> or less live with.
>
> Jim
>