1999 k2500 suburban fuel mileage

[derekbell2605]

Anyone have any suggestions for getting better fuel mileage out of the 5.7l? My first tank was decent at 13 mpg but this last one was down at 9.5 mpg. 180000 miles on it most of the second tank was city driving so I don't expect to get that all the time just wondered if anyone had any advice thanks.


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[aardvarcus]

When I was daily driving my 1991 K2500LD with the TBI 5.7l, I tried several things to increase the MPG. By far the best was removing the 4l60 Auto and installing a NV4500 manual. That got me from 12-13 highway up to 15-16 highway and I eventually made it to 18MPG highway. How you drive it really matters, and a stick enables you to have more control. Other than that you can follow the basics for MPG such as don't haul unnecessary weight, make sure your tire tread pattern matches your use (don't go super aggressive unless you really need it, that roaring noise is wind drag), don't add on unnecessary parts that will cause aerodynamic drag, make sure you still have your factory air dam installed. Change out your fluids for high quality synthetics (especially helps on cold starts), and make sure all your factory emissions equipment is functioning (EGR, O2 Sensors, etc). Those are the simplest things that would make a difference.

 

[Martinjmpr]

When I was daily driving my 1991 K2500LD with the TBI 5.7l, I tried several things to increase the MPG. By far the best was removing the 4l60 Auto and installing a NV4500 manual. That got me from 12-13 highway up to 15-16 highway and I eventually made it to 18MPG highway.

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How difficult was that swap? From what I've seen the auto-to-manual swap is one of the rarest in the truck/4x4 world. Manual-to-auto seems common but going the other way is very rare. Did you have to put in a different ECU or anything?

 

[aardvarcus]

The 4L60 (non electronic not 4l60e) to NV4500 is just about the absolute easiest manual swap possible. Just change the transmission and transfer case out, add a clutch petal, and a few assorted odds and ends. Don't even have to change driveshafts. You don't have to change anything electronic with the 4l60, but some things like reverse lights and neutral safety switches should be swapped over which require different connectors if I recall. If you have the 4l60e you may have to change the ECU, on some of them you can get away with tricking the truck to thinking it is in neutral the whole time, I don't remember for sure. I dug up my old build thread below, you can see my writeup of the swap there. (The truck and transmission is still going strong, I just don't drive the truck much since I got one better on gas.)

http://www.expeditionportal.com/for...quot-Redbird-quot-Build?p=1436164#post1436164