I'm looking for a relatively fuel efficient truck, with a bench seat that comfortably fits a man and two women. I did some research, and of all trucks that get 25 MPG highway or better (and can be had for less than 5K on average) the 1st gen Dodge Dakota has by far the widest front seat. If you think I'm wrong, let me know - it's very possible that my data source is off.

With the use case established, I noticed that there are some fairly wide swings for the highway MPG rating from model year to model year. The list is below and it's based on the 4cyl manual.

Yr = Year, Fe = Fuel Efficiency, En= Engine
Yr Fe En
88 26 2.2
89 26 2.5
90 26 2.5
91 24 2.5
92 24 2.5
93 25 2.5
94 25 2.5
95 25 2.5
96 23 2.5

Why does the highway MPG vary so drastically despite all trucks having the same 2.5L engine (after the 88 year)? I figure maybe the tune changed, or the later model years have a more default equipment and therefore weight. Or maybe the EPA's tests changed from year to year.

Because of this I've been very interested in the 89 and 90 model years but depending on the reason for the variation, I might cast a wider net.

 

The tune. And emissions laws.... 96 was the first year of OBDII.

 

Would it be possible to change the tune by swapping the cam and/or ECU from a junkyard 90 onto a 96? ODBII with 26 mpg would be pretty great.

 

Nope. The OBDI computers were not flash programmable. WAY to many differences in the way things work.

 

So the ECU is a nogo. If my 89 2.5L engine bites the dust and I need to replace it, can I grab an engine off of 95 and drop in the 89's camshaft and hook up the existing 89 ECU and still get that sweet sweet 26mpg? Most interchanges list the 89 2.5L engine as interchangeable up to 95 or so, so I think I can get away with it

 

Are the gear ratios any different in the manual transmission through the different years? I don't know much about the 4 cylinders.

 

The 95 2.5 is a direct swap so you won't need to worry about anything, the interchange says it's the same engine. As for mpg differences I doubt that you experience any difference at all, the epa numbers were not very reliable anyway IMO.

Steve

 

I'd like to know the same info....I get mixed numbers on AX15 internals and so I don't really count that as reliable, and then there are different applications. Jeep people list some different gear ratios as well.

And then there's the standard FD...which was suggested was the 3.21..but who knows if that's true and figuring out which you have by pulling pumpkin cover is oh so much fun.

Steve