|
You should look at replacing all of the fluids with the good synthetic stuff for starters - you have a lot of fluids that contribute to drag.
I took my driving test as a teenager in an '83 GMC 3/4 ton van, LOL! It had a 305 4V, and I got around 18-19 mpg regularly. In my opinion, 20 in your van should be simple. Look at the list of the 65+ mods, and you should see a lot that apply. Mirrors, wheel covers, lowering, etc. Tires would make a huge improvement as well.
Another item you can look at (I always wanted to and never did) is removing the factory drip rail. If you shave it off, make sure you weld the seam before you fill it, since I think it's a crimp fit in the rail that holds the roof on.
__________________
|