Just achieved 27 mpg!

[MAX A/C]

Hi Ya'll--

Wife and I just returned from a two week trip covering 4700 miles. We cruised around Yellowstone (and to Jackson, WY) for 4 days. The speed limit in Jellystone is 45 mph, and frequently you're behind someone rubbernecking while driving at 35-40mph. Anyway, we went 454 miles on 16. 8 gallons of the smelly stuff, for a mileage per gallon of 27! That's with a 4x4 club cab, (and at 7000-8000 feet elevation) so I'm pretty happy. Previously recorded a best of 26. 3 cruising around Durango, but that wasn't really a long enough distance to be a good solid reading. 48-49 mph is peak torque in 5th gear(1400 rpm) which is where I spent most of the miles, downshifting frequently for the grades or slow drivers. I had the valves adjusted at Cummins Southwest just before leaving, and I recorded slightly better mileage than ever. 14. 5 to 17. 5 towing our small 5th wheel (5000 lbs) depending on headwind or not, and speed (55mph seems to give 1 to 2 mpg's more than 65 mph).

 

[JFitzgerald]

That's pretty cool with a big heavy truck that can tow just about anything, isn't it? I am getting about 18. 5 MPG with mine. This is with what I call "country miles", not city, not all highway either. Also had the A/C on a lot lately. The previous owner put 285-75R16's on the truck. They are not much taller, but wider. He said he lost a couple MPG after installing them. I'm thinking about replacing them with a skinnier tire. Anyone else have any experience here? Makes me wonder because a friend has a '92 W250 standard cab, auto, 3. 54, standard size tires, and claims 22 MPG. Don't get me wrong, I am very happy even if I don't ever do more than 18. 5, just curious. My truck came with a set of stock size (235-85R16?) tires, wheels and hubcaps, so I will try them first to see if there is a difference.



By the way, what size fuel tank on my truck? 24? Someone told me the Club Cabs have smaller tanks.

 

[Bob Beauchaine]

H Scott

Congrat's on those numbers! I have found that my best mileage numbers have come on the first tankfull after I've just finished a long tow. I don't really know why but it seems to work that way.

Happy Trails

 

[MAX A/C]

Hi JFitzgerald-

Your factory tank is 30 gallons. I don't know how that compares in size to a regular cab. Regarding the tire size, I'm surprised the 285's cost 1-2 mpg's (if they are the same diameter as whatever size delivered 1-2 mpg better). I'm running 235/85's now, look a little small for the truck, maybe will go to the 285's when these wear out.

Scott

 

[drives mopars]

93 mpg in dually

my 1993 4x4 dually ext cb



14 loaded 17 to 19. 5 cowboy hwy



3. 54 5 spd



my bro's 99 4. 11 a/t 4x4 gets 14-15 empty



maybe 16 hes got it raised and bigger tires

 

[Gary - K7GLD]

Scott sez:





"I'm running 235/85's now, look a little small for the truck, maybe will go to the 285's when these wear out. "



I use the 235/85's too - can't really say they look "small" on my truck - but tire salesman here tell me that I already have the largest size that will fit properly on my rims and still fit inside the wheelwells - especially in sharp turns. Let us know if you are successful in mounting the larger size...

 

[Matt S]

Congrats on the mileage. My best is on highway trips I am getting 22 mpg. Looks like I need to get my timing checked. Do you know what your timing is set at to get 27 mpg?

 

[JFitzgerald]

Originally posted by Scott Morgan

Hi JFitzgerald-

Your factory tank is 30 gallons. I don't know how that compares in size to a regular cab. Regarding the tire size, I'm surprised the 285's cost 1-2 mpg's (if they are the same diameter as whatever size delivered 1-2 mpg better). I'm running 235/85's now, look a little small for the truck, maybe will go to the 285's when these wear out.

Scott

When I first filled it, the low fuel light was on, the gauge was near "E", and it took about 21 gallons to top it off. Maybe my sender is saying "low" too early??



The 285's measure about 1/2" larger in diameter, but are a couple inches wider. Maybe the previous owners' figures are off. I will try the original sized tires to compare.



Thanks Scott.

 

[Midnite]

Originally posted by Matt S

Congrats on the mileage. My best is on highway trips I am getting 22 mpg. Looks like I need to get my timing checked. Do you know what your timing is set at to get 27 mpg?

I was thinking about this as well. I'm getting about 15 -16 in town and maybe 18 highway, and I'd love to see if I could hit 20. How much could resetting the timing improve things, assuming the pump is currently set to Cummins' specs?



Mike

 

[MAX A/C]

Originally posted by Matt S

Looks like I need to get my timing checked. Do you know what your timing is set at to get 27 mpg?

Matt and Midnite--

Sorry, I dunno what the timing is set at, I've never had it looked at or messed with, so I'm assuming it's at factory specs. I bought the truck used, so I really can't say for sure it's at the stock specs, but I'm guessing it is, as everything under the hood was absolutely stock when I bought it.



I really think the key here, assuming everything is adjusted right, is to putt around at peak torque (no higher). It's not something we do on a daily basis, as the road speed is too slow. But it was interesting to see what the engine is capable of when taking it easy!

Scott