Quote:
Originally Posted by Old Mechanic
One thing to consider is the time factor. Higher speed when climbing means less time at the much lower mileage than your average for the whole trip. While your mileage might not be it's highest climbing at higher speed, your time suffering through that lower mileage is less and therefore you will have an overall average higher by spending less TIME making the climb and MORE time at higher mileages.
I may be crazy but I'm fairly sure the time factor at much lower mpg is something to consider as well.
Maintain the best load in gear until the grade forces you to loose speed, then use the next lower gear to maintain the best load, but also make the total climb as short as practical. Not crazy different but err to the practical but shorter (time wise) climb.
This assumes the coast downhill will not force you to sacrifice your speed for staying legal as far as speed limits. Most of the hills here are not steep or sustained and when I can do so without aggravating others my speed will be lowest at the top of the hill, allowing me to reach my peak speed without risking a traffic ticket.
With lower grades, I try to keep my downhill speeds close to the limit in traffic and I can do this on the Interstate in 65 mph traffic, pulse drafting a big rig. I did this today going to the dentist and when I got there I was reading 61 mpg for 25 miles without causing any problems with other traffic.
regards
mech
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Yup, yer crazy. The fuel economy method ground vehicles use is in miles per gallon; how ever long that takes. Contrary to your thinking, one usually uses more fuel not less by going faster... to cover the same distance. "Suffer" with the lower speeds and save fuel or go faster and suffer poorer fuel economy to go a given distance... your choice. But the idea generally promoted around here is to use less fuel.
Gallons per hour is the method aircraft use to calculate economy because the time/speed in the air does not always correlate with the distance traveled over the ground.
Aircraft try to maximize the amount of TIME they can spend in the air on a given amount of fuel and ecomodder ground vehicles try to maximize the amount of MILES they can cover with a given amount of fuel.
Minimizing the time in either case uses more fuel... that means going faster. And the aircraft won't be able to spend as much time in the air and in the case of ground vehicle, it won't be able to cover as many miles with its allotment of fuel.
Speed Kills.