What speed is most fuel efficient?
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From: Crestone Co
milage for a stock 02 ,3500, auto with cabover
I get about 12.5 running between Crestone and Taos, RPMs 1700 to 1800 and speed about 60 to 65 mph .But I'm carrying a lance 1030 ,total load 11000 lbs; Revos , 65lbs front, 60 rear. The hills kill me. I'm thinking of adding air at least to the rear and cleaning the sensor , see if that helps.
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From: Cummins Technical Center, IN
Originally Posted by supr
My truck is just getting broken in. I am normally always towing a heavy 5er, so wind is a factor, as is height; the 5er is 12' high. I have tried slowing down to 55, about 1750rpm with 4.10's/6 speed HO. I have broken 13 mpg on this last trip, about a 14k trailer. I think 55-60 is optimal, with or without trailer. Have K&N, may help a little. I also keep tires aired, 75 front, 70 back. Also have 5th wheel tailgate, also may help a little with wind resistance. I think 17 is about normal for me,solo, at 60-65, 2k+ rpm. Many guys have said 1800 rpm's works well for them.
I'd think that a 5ver tailgate doesn't help much with wind resistance, compared to the huge trailer front blasting the wind.
17 Solo wih a 3500 and 4.10s isn't that bad. I'd think that's about as good as you could expect.
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From: Cummins Technical Center, IN
That's the beauty of 2wd.
I've heard many stories of 12Vs getting 28mpg at slower speeds. A 2wd 2500 3.54 axle reg cab truck should be able to get really good hwy mileage if tire pressure and such is addressed.
I've heard many stories of 12Vs getting 28mpg at slower speeds. A 2wd 2500 3.54 axle reg cab truck should be able to get really good hwy mileage if tire pressure and such is addressed.
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From: Southwest TX, BFE
4.10 gears aren't the end of the world...
I have a 2001.5 Reg Cab 2500 4x4 with the 4.10's and I run 315/75R16 tires on it. I went from between 16.5-17.5 mpg with 285/75R16 tires to a high of 19.7 mpg with the new 315's. I think those of you running a similar setup can GAIN mpg with an increase in the tire size, contrary to popular thinking. I did a lot of research regarding axle ratio vs. RPM vs. tire height to find what would get my RPM's down and increase mpg. The only way to get the 4.10 rear end to come close to the 3.54/3.55 setup that others have is to increase tire height to drop the gear ratio. I did some checking and my gearing is now down to 3.61, so I'm happy with the lower RPM's. I don't know if I'll EVER get 21 mpg but I can live with the 19-20 mpg and I haven't even tried to keep it at a steady 60 mph. The majority of these mileages were taken on trips at 65-70+mph. Oh, and I've had over 18 mpg in city driving with the larger tires too. So, to those thinking that 4.10's mean having to park the Ram, THINK AGAIN!!! And, here's a tip for those who have the 4.10's but run a 4x4 dually, you can drop your gearing by running LT255/85R16's on that setup. Those are narrow enough and tall enough to make a significant difference. Hope this helps 
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From: East Central OK
Originally Posted by HOHN
It's interesting to see how much different the 12V BSFC curve is compared to the 24V, and explains the better mpg. Anyone want the 12V numbers?
JLH
JLH
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From: Cummins Technical Center, IN
They both the VE and P-pump numbers. The P-pump is best in terms of BSFC. VE pump is close to 24V BSFC.
P-pump engines are most efficient at 1600rpm. 24V vp44 engines are best at 2000rpm.
General rule of thumb-- the wider the RPM range an engine has to operate, the less efficient (in terms of bsfc) it will be at it's peak efficiency.
The MPG king of all CTDs should be a reg cab 4x2 12V (p-pump) with the cruise set at 1600rpm.
jlh
P-pump engines are most efficient at 1600rpm. 24V vp44 engines are best at 2000rpm.
General rule of thumb-- the wider the RPM range an engine has to operate, the less efficient (in terms of bsfc) it will be at it's peak efficiency.
The MPG king of all CTDs should be a reg cab 4x2 12V (p-pump) with the cruise set at 1600rpm.
jlh
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