I recently replaced my fuel pump assembly with an Delphi unit. In the process of monitoring the accuracy of the fuel gauge I decided to check my MPG for a few tank fulls. My first check I got 19 MPG and I filled up yesterday and the result was that I got 20 MPG. This is in my 89 GMC Jimmy 2WD, Auto, K&N Air Filter, Injector Pod Spacer, Stock Exhaust with a high flow CAT, and Michelin tires. Most of my driving is highway and I use my cruise control as much as possible.

 

wish I got 20 mpg

 

the uses synthetic oils in the rear diff may net you a little extra, also better cool, wires and plugs, cap and rotor, last but not least don't forget to check the vacuum lines for dry rot the more efficient it runs the better gas mileage can be all the little things tend to add up over time, good luck on increasing your fuel mileage

 

i just figured mine out. 1994 cpi. 4.3 litre
415000km on the engine.

getting over 18mpg all around. highway i bet it's nearly 25mpg.
have a few things yet to do.
cap and wires surely. haven't even used sea foam yet. ha! that'll be a decent help