If one were looking for the best possible fuel mileage cummins in-line six... which one is the best?

1. First Gen
2. Second Gen
3. Third Gen

I bet the V-8 diesel guys are wishing they bought something different.

 

well i know my truck gets about 23 on the highway and 20 in the city. and thats with the non OD 727. my dads powerstroke gets about 20 highway and 18 city. not to abd for a v8. not a friend of mine gets about 8 highway and 6 city hahahah he likes to blow ALOT of black smoke out of his second gen hahahaha

 

My '93 dualie was getting 18-19 in town and 21-22 highway empty, and 15-17 pulling my 10K 30" 5th wheel trailer... With 238.4 RWHP on the dyno

 

first gen....
rotary pumps are more efficient in my opinion.
Best of 24.8 in mine, average 60mph

 

1st gen D250 with 3.07's and a 5 speed.

 

yes, if you want to get the best MPG empty even consider getting some taller/skinnier tires in the rear like 255/85r16 or 245/70R19.5 pump them up to the max for less rolliing resistance and you'll definitely see gains!!
But yes I concur that a first gen engine with the VE rotary pump will be the best fuel miser...

 

Thank you all! Good stuff..
I should probably learn more about the ve rotary pump and why this design is a better fuel saver.

Regards
Tom D

 

I get 15 mpg.....

 

I get 15 in town, 22 hwy @ 65

 

I get pretty good mileage empty close to 800km to on a tank hwy

 

I average about 19-20mpg, I'm not complaining especially with 4:10's

 

I agree with the 1st gen comment, especially the d250 with 3.07 and 5 speed. Through some super pizza cutter tires on it and you would be set. But also kind of depends on what kinda of money you spend and how mechanically inclined you are. A first gen is the cheapest but its all wrench pulling. A 24 valve or CR cost more to make good mileage but its for the most part can be plug and play. IMO

 

Not as stringent of emission requirements as the 24 valve engines.

The design of the pump allows for advance as RPM increases, similar to the distributor on a gas engine, meaning you use less fuel than a P-pump (which has no RPM advance) at lower RPM to make the same torque. This in turn equals less fuel used.

 

Dingdingdingding..... We have a winner! The '94-'98 trucks are stuck with the same timing at all engine speeds. What would be optimum timing at highway speed is too advanced for easy starting and good low RPM operation. So for fuel economy, the VE pump is better.

 

Awesome!! Thanks Again!