It depends on the engine, the gearing and the wind resistance. The latter
tends to dominate since it goes up exponentially with speed. The best engine
speed is usually low RPM but not necessarily the lowest; most (gasoline)
engines run more efficiently around 2000-2500 RPM than they do at 1500. This
"most" excludes Diesels and old fashioned pushrod monster displacement V8s.
You want to drive in your tallest gear, at the lowest speed that enables the
engine to rev into its efficiency range. While it depends greatly on the car,
the cars I've owned seem to do best from 50 to 70 mph.
Drive up at Tahoe sometime (in the summer, on clean dry roads) and you'll
probably notice that you get better fuel economy up there. The air isn't that
much thinner, but it's enough to make a difference.
Interestingly, speaking of engine efficiency, you'll find that some cars
actually get better mileage with bigger engines. Compare the Lexus GS300 and
GS430, for example. The only difference is the engine, a V8 vs. a straight 6.
And the V8 gets the same or better fuel economy (not to mention that 300 hp
makes it more fun to drive).
-----Original Message-----
From: owner-ba-autox@autox.team.net
[mailto:owner-ba-autox@autox.team.net]On Behalf Of Phil Esra
Sent: Friday, February 09, 2001 12:59
To: ba-autox@autox.team.net
Subject: fuel mileage
miscellaneous musing:
I was just wondering, and thought maybe someone here would know. What is the
most fuel efficient speed to drive at? My guess is that it would be at
whatever speed you're in your highest gear with the engine turning as slowly
as possible. But is wind resistance great enough that that's not true? Any
thoughts?
phil
(ps--got the bearing replaced, thanks for all the advice--made it home over
the bridge with no drama--had to replace the hub too, $492, ouch...)
_________________________________________________________________
|