How much fuel economy one gets is, to a large extent, determined by how one drives. Slower = better economy.
That being said here are a few mechanical items that can, and have helped my 2002 V6 4.0L 4WD Ford Explorer:
1) Tire inflation pressure. Insure you are running at least as much as Ford recommends for your car. The higher the pressure in a tire, the less the rolling resistance. More than 2 or 3 pounds over one will start to effect the ride (harsher) and increase the bounciness and chances of rollover. In any case do not go over the maximum sidewall on the tire. I'm running at 32/37 and my Explorer which is spec'd for 30/35.
2) Engine oil. Insure you are using the right grade and change it every at least every 5000 miles. To really know how the oil is doing, get a used oil analysis and change according to those results. Using a synthetic may also be of benefit in MPG, and can certainly vastly increase the oil change interval (although I'm using regular yellow bottle 5W30 Penzoil in mine).
3) Put synthetic oil in the front differential, rear differential and transfer case. I used Valvoline SynPower 75W90 gear oil in my front differential, Lucas Synthetic 75W140 limited slip gear oil in the rear and Mobil 1 Mercon V Synthetic ATF in the transfer case. I'll be doing the transmission with the Mobil 1 soon.
4) Change out that PCV valve! No telling when it goes bad, and it is super cheap so why not? If bad, it will decrease gas mileage, cause sludge and a host of bad issues over time.
5) Change out the spark plugs for some new ones, but at least insure that the gap is in spec. Use double platinum or iridium.
6) Check the spark plug wires.
7) Change the air filter. Won't effect mileage in an OBDII vehicle which has a MAF sensor and always insures the proper fuel/air ratio, but limits the max power of the engine.
8) Go to
www.cleanmpg.com and learn the techniques on how to drive for good mileage. Some of the techniques are radical, so do only what you feel comfortable doing. On the highway the biggest increase in mileage comes from driving less than 60MPH. I drive at 57MPH and get 24MPG out of my stock 2002 Ford Explorer V6 4WD.
Rumple
I want to do more economy, my EX is very "thirsty".
Alberto