Engine/Transmission (1994 - 1998) My 12V MPG

[The patriot]

1800 whatever RPM will still be WAYYYY under 70 MPH.

 

[radixr]

Sell my 12-Valve?

There is no way I would sell my 12V for a new engine. I get 22-24 mpg (empty) and from what I hear, the new engines can't even come close. Not only that, they don't sound like a real diesel. Oo.

 

[ksoren24]

My speedo is correct, I checked it with a gps, I can't explain the rpm either, maybe when the transmission was rebuilt something was screwed with, I don't know. Or maybe the tach is off?

 

[travis97cummins]

19 mpg is the best ive ever got with my 97 its got 354 gears and 315/75-16 hankooks, 22 mpg with the 96 its got 354 gears and 285/75-16 coopers, 22 is the best ive got with the 00 its got 354 gears and 285/75-16 wild spirits

 

[travis97cummins]

just got the versatile so dont know about gph

 

[abranz]

I only wish I could see over 20mpg in my 96 and I don't even push it over 70. Have never figured out how other 12v's do so well. The 06 does better by about 4mpg figured accurately. Anthony

 

[CTaylor]

I have been getting right at or just under 23 with my 97 12 valve with 5 speed and 3. 55s. I do short trips in town at around 55mph also and drive her hard

 

[SSage]

I find if my rpm stays at 1750 or below I get 19 mpg or better. I'm a bit heavy though with tools, another 200 pounds or more of work materials, a high rise camper shell, ladder rack, ham radio antennas, steel brush guard, diamond plate running boards etc. .



The way I'm set up now I can run with very light smoke to none at all with the valet switch and still let the coal roll when I feel like it. The truck got 23 mpg bone stock with the camper and brush guard... When working on the road driving the back roads 20 mpg is not hard to accomplish. 1750 is the sweet spot, slower and the egt's climb, faster and the fuel burn climbs... GPS says its around 62 mph, speedo reads a touch below 65 mph so its pretty close to GPS. I'd say its 3 mph optimistic...

 

[The patriot]

I noticed that my MPG's are better on back roads than the interstate.

Around here, if youre not running it @ 2200 rpm's youre gonna get rear ended.

 

[JerryNelson]

whats the best R. P. M. to run at

 

[surfbeetle]

The Cummins likes the 2,000 rpm neighborhood the best and for those of us with the NV4500 Five speed, anything over 2,000 rpms keeps the 5th gear nut happy.

 

[DRAG DIESEL]

whats the best R. P. M. to run at

This really depends on what your timing is set at and what turbo mods have been done. For a stock truck I don't have a "exact science" chart or anything, but higher timing is more efficient at higher rpm's. With stock timing i got the best milage keeping it around 1700 to 1800 like most have here. When I stepped it up to 18* 1900-2000 became my magic number. I regularly get 20. 5mpg hand calculated combo driving in my '97, and got 26mpg on my last trip to phoenix which was 100% hwy.



When I put the tighter converter in, I will probably step it down to 16-17* cause the rpm range will drop for most of my average driving. For now, 18* seems to be a good match with the stock converter and my driving style.