Originally Posted by highonpottery

18.5mpg is pretty good for a 4wd brick with only 90hp to push it around. like others have said, start at the engine and make sure she's running in tip top shape - so do a full tuneup even though your rig is only a baby with little over 100k on it, it's 24yrs old and sat for a good amount of that time with so little mileage.

i believe mythbusters proved the tailgate-down theory to be defunct and you actually get better mpgs with it up, since it creates a bubble of air = less drag. less weight overall in the rig will improve mpgs for all vehicles. make sure tires are not under-inflated. make sure wheel bearings are packed with non-24yr old grease and with the correct amount of preload on them. check to make sure all your diff trans and tcase fluids are in spec and not the original fluids. back off of the skinny pedal every now and then. coast as much as possible especially when coming up to red lights. driving like an old man vs driving like you stole it will significantly increase mpgs. run some injector cleaner or seafoam the engine, clean out your intake plenum from all the carbon/oil deposits. if you can afford it, do a CAT-back system for increased flow. make sure your stock paper air filter is fresh - it filters better than aftermarket and if not dirty flows decent too. wash your rig every now and then

all those little things you can do will help get you better MPGs even though you're pretty good as-is. my truck gets around the same as you for hwy driving, but i like to use lots of skinny pedal and my truck is a few inches taller/more wind resistance. good luck!