I was trying to hit around 2000rpm in cruise but it equates to 110 km/h ( a little fast for the wife!)I think that's about 65mph? thats in 5th gear if I choose fourth I rev at 2300 to run the speed limit. I have 285 for tires so they are a little tall ( same as a 33). Thoughts what works for you guys?

 

Give her some valium ....... or slow down.

 

Most second gen's like to run about 2000-2200 RPM's for maximum effeciency when towing.

 

My 95 liked to run 1800.

 

Best BSFC for 24V is 2000 RPM

for 12V, best BSFC is 1700rpm.

 

I've found the on-board computer to be way off, since I have injectors, Edge EZ, etc., and 19.5" tires. Last summer, carrying my 9'10" Lance camper, and towing a 15' tin boat (aluminum) I averaged a measured 14.2 mpg on a 2 month/14,000 mile trip. On shorter trips of 1,000 miles or so, with just the camper, I average a measured 12.2 - 12.6 mpg. Hmmmm.........?? I believe the reason for this is that on the longer trip with the boat, I was cruising at 60 - 62 mph almost the whole way, which, I think, is around 1700 rpm with my 3.54 gears. With just the camper, I run at 70 - 80 mph, at over 2,000 rpm. The sail factor of the big camper at those speeds has to be killing the mileage. Whatever the speed, if I watch the (inaccurate but consistent) computer, mileage is best under light load (duh ! ! !) and poorest with a heavy foot. In real life, this means downshift when the turbo starts to really spool up and egt's rise. Lots of revs with a light load, and low revs when cruising easy average out the best for me. Lar.

 

BSFC is a new acronymn for me... anyone care to extrapolate?

I like 2000+ on my 2003.

And since I don't have too many choices with an auto and 3.73 and tires that just don't match that setup... I'd rather run at 2300 than 1700.

 

Best Stinkin' Fuel Consumption....

 

My 98 RAM 2500 HD, 24 V Cummins will run at 71 MPH at 2000 RPM. That is a little to fast when pulling my #10,500 fifth wheel camper. Exception to that rule is when on really OPEN road sections, I will do 75 MPH. My truck tires are slightly oversized at LT 265/75 R16E. Milage around the city is 15-16 , on the open road, about 20, but pulling the camper we usually get 13-14 MPG. Only engine change has been a K&N air filter.
Fireman Ken

 

B.S.F.C.
Brake Specific Fuel Consumption.

It's a term Cummins uses to determine fuel consumption at certain RPM's for different engine configurations.

 

Does that apply only when towing. I can tell you that my MPG are much better at 55 MPH and 1700 RPM in 6th than at almost 70 MPH and 2000 RPM.

 

towing my 12000 5er, the lower my rpm's the higher my fuel milage.........JIM

 

i try to keep mine just under where the cops don't get me!!

 

2001, 6spd, 4.10 LSD, 4x4, 91/2 Lance cpr, towing 26' boat at 2000 to 2100 rpm. I get 13 to 13.8 mpg. If I go over 2100 the mpg's really start going down fast.

 

I have found that with the 4.10 gear unloaded I get 19 all the time and 20 on the flat lands. The 7% grades up don't quite make up going down for some reason. The best speed for my truck is 63mph 2300 rpm. If I go to 65+ the mileage drops fast to about 18 unloaded. Up to about 5000# I get 15 with out a problem again speed is the killer. It would be nice to have the 3.73 or higher for cruising but for pulling up the hills you can't beat the 4.10. Also here in TN with our infamous traffic, granny low is great for saving the clutch and you can often just idle in granny or 2nd.

Over all the 2200-2300 rpm seems the best what ever gear is used, and what ever load is pulled.

JMHO and dollar's worth.

bentwings