finding right cruising speed for economical gas mileage
We just purchased a used 2008 Winnebago View with 5400 miles. Does anyone know a good speed to travel at to get the most out of the mileage? It is a V-6 diesel motor.
Forum Discussion
A lot of interesting experiences here. When trying to push a garage door into the wind, try to make the wind slower. I've been in the RV/4x4 biz for a lot of decades and remember the results of a study about what was the best mileage per gallon of the then current (I'm guessing 1953) automobiles. After much testing, the best mpg was attained @ 43 mph. This is the cutoff on where wind resistance made less difference. I don't know why that stuck in my mind but I have my own experience with a smallish Lance truck camper mounted on a diesel pickup. My experience was similar to the diesel types above in terms of speed v. mpg. Simply, the slower I went the better the fuel mileage was per hour. We recently did a trip over the Mojave Road and were motating maybe 15-20 mph for days on end. I drove three solid days on about 1/4 tank of fuel. About 22 hours on 9 gallons of #2. So, it depends. In Afton Cyn:
The slower you go, the better mpg you get, to a point. Once you have lost the headwind, it makes no sense to go slower yet.
A gas vs. diesel engine have differing curves of that ultimate 'sweet spot' where you get the most speed for the least fuel expenditure. Most of that traces back to where the engine of note makes it's peak torque. On my Dodge Cummins, HO, 6 speed manual, the sweet spot has more to do with the rpms than the headwind. My personal sweet spot for the engine and how much frontal area i have and how much gross weight i have (10,200 pounds) is when the engine is running at 1850 to 1950 rpms. Even though the peak torque is at 1600 rpm. The earlier 12 valve Cummins 6BT made it's best at 1600 rpms. Bump stick and valve timing, plus the differences in injector pumps and compression ratios make the differences. With a gasser, the rpms are usually up higher with modern engines to get to the sweet spot. Still one of my favorite gassers is the tried and true GM454 and its offspring. You need to learn to play it like a violin, but some pretty impressive mpg's can be had, under circumstances you can control, if you can 'feel' where the engine/trans need to be humming. It boils down to a Zen thing. You need to breath with the engine. Feel what it feels. Let'er go down hill. Ease up when climbing. If you know what you are doing you can do better than your factory cruise control. I had a friend who used a manual throttle cable when driving long distance. Kind of dangerous in traffic, but he proved he could go with the flow and get astounding mileage on his Cummins powered pickup with a camper in the bed.
The sad part is you can't teach this 'feel' business. You just need time in the saddle and keep track of your mpg's.
regards, as always, jefe
The slower you go, the better mpg you get, to a point. Once you have lost the headwind, it makes no sense to go slower yet.
A gas vs. diesel engine have differing curves of that ultimate 'sweet spot' where you get the most speed for the least fuel expenditure. Most of that traces back to where the engine of note makes it's peak torque. On my Dodge Cummins, HO, 6 speed manual, the sweet spot has more to do with the rpms than the headwind. My personal sweet spot for the engine and how much frontal area i have and how much gross weight i have (10,200 pounds) is when the engine is running at 1850 to 1950 rpms. Even though the peak torque is at 1600 rpm. The earlier 12 valve Cummins 6BT made it's best at 1600 rpms. Bump stick and valve timing, plus the differences in injector pumps and compression ratios make the differences. With a gasser, the rpms are usually up higher with modern engines to get to the sweet spot. Still one of my favorite gassers is the tried and true GM454 and its offspring. You need to learn to play it like a violin, but some pretty impressive mpg's can be had, under circumstances you can control, if you can 'feel' where the engine/trans need to be humming. It boils down to a Zen thing. You need to breath with the engine. Feel what it feels. Let'er go down hill. Ease up when climbing. If you know what you are doing you can do better than your factory cruise control. I had a friend who used a manual throttle cable when driving long distance. Kind of dangerous in traffic, but he proved he could go with the flow and get astounding mileage on his Cummins powered pickup with a camper in the bed.
The sad part is you can't teach this 'feel' business. You just need time in the saddle and keep track of your mpg's.
regards, as always, jefe
