Hello all. My current ride is a '95 Chevy k2500 with the 7.4 gasser/auto. This truck has been a very good truck and tows well. The down side is that it gets 10-11 mpg hwy and probably 8-ish in the city. I will be selling/trading this truck in the near future and I'm trying to plan ahead and start gathering parts for a swap. My question is; can I get 25 mpg in the city from a full size truck with some sort of diesel engine? I'm not really interested in the popular cummins swaps but I don't know what all engines are available to swap. I'm not going to hot rod the truck but it will need to be a daily driver in the city. My only requirements are that it be smooth running and not real loud. Any one have any ideas on what a good engine would be? Am I asking for the impossible? Don't hold back on your thoughts on this. My goal is to have a nice truck that gets great mileage. Thanks!!

PS.
I'm open on make and model of truck as long as its a full size 4x4.

 

I get 21 on good days and 19 on bad days and my truck weighs 9600 lbs

 

Not since the early 90s. A good running stock D250 1st Gen with a Getrag would do it driving empty carefully. Nothing since.

 

I have a buddy that swapped a 4BT into his 3/4 ton dodge two wheel drive. The truck originaly had a 5.9 gas engine and a NV4500. I know you said you weren't interested in doing a Cummins swap, but his truck averaged 26 on the freeway driving reasonably.

 

The 4bt was a route that I was interested in looking into.......until I heard/saw one running. My buddy traded around and got an old delivery type van. It had the 4tb and an automatic in it. Now I don't know alot about these engines but this thing was very rough running. I don't mean rough like it wasn't hitting on all 4 but like it was vibrating and shaking all over the place. Thats just not what I'm looking for.

 

You are aware that you can add a balance shaft to the 4BT? The insulators also play a big role in transmitting vibrations to the interior compartment.

 

Ditto^^^. Those things run A LOT smoother with a minimal amount of work and good insulators(engine/trans mounts). Add a balance shaft and have a machine shop balance the rotating assembly.

25mpg city isn't doable without an engine swap, other than the 1st gen dodges which aren't going to be anywhere near as comfortable as your 95 2500. Do you want to just swap something into your current truck or find a different truck?

The only other diesel for a swap the I know of to consider is the 2.5L I5 from the Dodge Sprinter vans. They use the 545-rfe 5 speed auto trans (same trans behind all the truck/jeep Hemi engines). It's a common rail injection system and makes plenty of power, astronomically smoother and quieter. The transmission has plenty of upgrades available but really doesn't need a whole lot, it's a good trans.

If you want a manual, I'm sure you could get a bellhousing or adapter to hang an NV4500 behind it but I don't know that for sure.

 

I didn't know about a balance shaft for these engines. Actually I know very little about a diesel engine but I'm trying to learn. I will be buying another truck to do this swap on. My current truck is a regular cab and I have a habit of keeping a truck for several years so I am thinking about an x-tra cab or short bed-crew 4x4. I have looked at the Sprinter engines and I saw a few on ebay but they are very expensive. These sound quite to me and seem to idle smooth but I have never driven one. This is not a swap question but Whit's post has me thinking now. Do you think a Duramax, 6.0PSD, or Cummins equipped newer truck could do 25mpg city? Every thing I read is about getting the most power and torque out of these engines but could you go the other way to get the most mpg? Sorry this is long, sometimes I start to ramble when I get going, .

 

The only way you will get that kind of mileage from any of the big three, is to put one of those engines in a very light truck. A 6bt in an S-10 comes to mind.

 

I agree, the only way to get better milage is to put the power of the larger diesel engines in a lighter truck body or put a smaller V6, 6bt, or 4bt into a full size truck. Changing your differential oil with a good synthetic oil reduces how hard the engine has to work to get power to the ground can help as well. You have options. The military used 4bts in their hummers for a long time and they are pretty heavy vehicles. My suggestion is a 4bt with all the balancing and such to make it a quieter, smoother ride or a 6bt which may be better but your milage will drop with it a little.