It would seem ideally that elevation rise and fall would not hurt fuel economy, or even could increase it. It would be similar to pulse and glide-a technique used in "hypermiling" to get good fuel economy.
Try as I may in the real world I haven't seen any gains from climbing a mountain and coasting down the other side. At best little or no loss.
In most cases this could be due to cornering and braking on winding roads. Also downshifting to minimize transmission hunting, or to retard speed.
My E450 doesn't appear to shut off fuel entirely at coast. I've had cars that did do this. One other element is the downshift to climb a hill increases engine speed and loss due to engine friction. Some engines also go into an fuel enrichment scheme at heavy throttle (it appears that at least some stock V10s do not).
I too am pleased with the performance and economy of the V10. These rigs are not aerodynamically sweet. Like others, I keep it at 55-60 and it will get 10 mpg under steady state cruise.
pnichols wrote:
I've always wondered why general mountain driving, properly done, should reduce fuel mileage very much.
Isn't the extra fuel one burns "going up" supposed to be close to exactly compensated for by the reduction in fuel burned when "coming down"??
As a supporting fact, I believe that modern (gasoline) engine computer control sytems shut off the injectors completely when you let up on the gas pedal ... so that when going down hills you're not even supplying any gas to keep the engine in an "idle state".
(This is ignoring loss of efficiency with increasing altitude when you're "going up". That's why I used the wording "close to exactly compensated" above, instead of "exactly compensated".)
