Tim9712v

I have a 97 Auto, 4x4, 4.10s, and 265s.

I get 15mpg, 15mpg in town, 15mpg on the highway, and 12-14mpg towing roughly 5-6000lbs. However I am pretty hard on it around town, and on the highway i am running near red line. I run about 80mph, running roughly 2700RPMs IIRC. Red lines right around 89-90mph. Maybe my ol' cummins is starting to get wore out at 306k, but I wish I got the mileage you guys are talking about.

Box5

no, it's just cruising much over 2100 will kill ur mpg ^. by the way how can u stand cruising at that rpm? I think i'd go crazy, lol.

wcbcruzer

I was thinking that as well. Although the RPM's are higher, it's easier on the engine to push the truck. So you might actually give it more fuel to keep the truck cruising at 65-70 mph with 3.54's than 4.10's.

cheapskate

so... you're telling me i don't know how to figure my fuel mileage? a steady 80 mph from indy to chicago and back = 21.333 mpg.

cheapskate

my average mpg for all driving is high 17's to low 18's though. worse in winter. 2wd and 3.55's help alot

leprechaun

Tim9712v:
If you slowed down to about 2000rpm's, your improvement in fuel mileage would surprise you.I have the same setup as you and if I set my cruise at 60mph [1800 rpm] on the interstate, I get 21 mpg.Running 65 mph towing my trailer on the interstate I get 13.5.I think I could do a little better at 60 mph but I have to keep up with my son-in-law.The right foot has a lot to do with your mileage.

Teddy Bear

I rode back home from Indiana from Scheid one year with Cumminsdriver. He was curious to see what his highway mpg was so we filled it up before we left Indiana. Got about 10 miles away from home and filled it back up again. According to my precise calculations he was able to get 22.8 mpg. Most of the trip we kept it around 75mph.

Hayseed

Don't know but I want to run some of Clutch's fuel, must be good stuff. I run pretty hard empty and loaded but I get 16-18 empty and 12-14 loaded. I usually gross around 23000 lbs loaded and run 2300-2500 rpm, depending on the road.

DRam11

Montana to Delaware and back with '97 4wd, 5 spd, interstates & state highways, cruising between 65 and 75 depending on the road and traffic. We averaged 21 mpg over 5,000 miles. It seems that speeds over 75 mph will drop mileage to 19 or so, keeping it at 65 gets up to 22. Last year we picked up a 34' 5th wheel, 8,500 pounds empty, and are averaging 12 to 14 mpg towing at 2,000 - 2100 rpm. I tried towing at 1700 rpm, but the engine seemed to be luggng and mileage dropped. I have 3:54 differentials, 2000 rpm is 65 mph, give or take speedometer error. No estimate for in town driving. I've never gone through a full tank in town to check it.

Clayten

Call BS if you want keep it under 1300 rpm shifting at no more than 1600 you can get 11 kilometers/ liter. And if you know how to use a diesel to it's full extent then you can do this. Cummins suggest to stay at or under 1300 rpm. I can get 10 klicks/ liter consistently on #2 mixed with PS.This is truck only. And I will take on any bets for your title against mine. If you dare to call BS on this I will sell your truck for my gain.

1320

At 10 klicks, thats 23.49 miles to the gallon.......@ 11 its 25.8.......not 27. Looks like betting is probably a good idea.

Clayten

My math comes out to 11 klicks/ liter = 26.29 us, 10 klicks/ liter = 23.9us. Here is how I got there.
http://www.teaching-english-in-japan...ters_per_liter
I never said 27, I'm still taking bets.

OutlawStorm

At 1300 rpm,, how fast are you going? 1300 rpm on a cummins diesel in a Dodge is Lugging it. Maybe 1300- 1500 on a big rig is ok as they have alot more gears than our trucks do. There is now way you can only be running 1300 on an interstate. My Cummins dealer told me to keep it around 1800 - 2000 rpm. Also on a Stock Auto trans 1300 is way to low of a rpm and it will heat that trans and destroy it,, There is not enough line pressure at 1300 to keep the convertor from slipping, and it will chatter and warp it, and not long after that you will be buying a new transmission

With your setup 1300 means you would be going 45 mph with the stock 245/75/16 tires

Box5

just idling in gear is almost 1300, lol. the 5spd would be near impossible to keep the rpms that low. And i'd think the mpg would be worse down low because most trucks with alittle power mods smoke like crazy if u bog it like that.

03qclb5spd

True, I can keep it going without bogging down about 1000, but the moment you lay into it, you can tell it's dying for you to downshift. It will dump smoke like mad from those rpm's.