I bought a '91 with realtively low mileage (56K) back in late April and I used a motor flush and changed the oil, tranny fluid and filter, fluids in the transfer case and diffs, cleaned the MAF, changed the plugs and wires, cleaned and relubed the brakes (pads were near new but vehicle had mostly sat for 2 years) cleaned and repacked the front wheel bearings, did the TPS mod and set it to .96v (Was .8v originally), removed the silenced for the intake, opened up the airbox and put in a K&N filter, removed the worthless luggage racks, lubed the front end and rear u-joints ....
Took a trip to Wisconsin Memorial Day weekend and got 21.9 MPG (10% Ethanol, 89 octane) and could have gotten better if I wasn't following a friend in a '97 F250 Heavy Duty with a camper on and pulling a boat so we were going fast downhill and then dropping back going uphills ... not the best on MPG (He got 11 MPG but only gets 12MPG unloaded)
On average (Mostly city driving) I was get 17.5 MPG but dropped to 16 MPG after fixing the A/C (and using it a lot) .... I hope to pick up a little after the valve body rebuild and shift kit (we used to gain a little putting them in my Dad's fleet of F250's back in the 80's) and a little more going to all synthetic (Diffs and transfer case are already syn) ....
None of the things I did in and of itself gain you much but the sum total obviously got me more than the average '91 Explorer owner ....
