1994 4.0L E-4WD Aerostar with poor fuel economy.

I'm only getting 13 mpg on mid grade gas. Previous '94 AWD got 24 or so reliably. Starts easily hot or cold, and has lots of power. I suspect one or a combination of the following: open thermostat (coolant only getting up to about 144 degrees on freeway with A/C on), coolant temp sensor, oxygen sensor. Wondering if the 130 degree switch from closed loop to open loop is at exactly 130 degrees, or does it vary? I picked up a Motorcraft 195 degree one that I'll likely put in tomorrow, then assuming it warms it up to snuff, I'll check the resistance on the coolant temp sensor. Hopefully, that will do the trick, but if not I'll look at oxygen sensor(s?). Any thoughts or suggestions are welcome. I like this van a lot, and I'll like it a lot more once it lightens up on the gas consumption. Thanks for any insight you folks can offer.
Ed

Welcome to this forum! The E-4WD will consume more fuel because it's heavier than the RWD version plus it has more moving parts. My RWD 1995 van gets 7 MPG in the city with stop & go traffic, stop signs, and traffic lights on every corner. We have a new 25 MPH speed limit which causes the traffic to move even slower than before. You basically just coast, and can't accelerate, so I wonder if that helps or impedes mileage. Clean the MAF sensor, O2 sensor, and throttle body intake. Check for vacuum leaks. Make sure that the air filter, and the PCV valve are clean.

Hi Brooklyn,
Thanks for the additional cleaning suggestions. Air filter is new, but I'll follow up on the rest. I don't want to settle for anything close to present mileage, as I got really spoiled by the ~24 mpg on our previous '94 AWD Aerostar. As they said back in the day, "Onward through the fog."

Did you check the tire pressure in all 4 tires? Are they the same number tires? What about the tread? Some tires have less rolling resistance than others. Under inflated tires cause more drag. Some vehicles use nitrogen instead of air in the tires, but they have to be refilled more often since nitrogen is lighter than air. I wonder why they don't use helium instead (maybe it might require more refills since it's also lighter than air)? How are the rear brakes? Are the shoes dragging? What about the wheel bearings (those 4WD hub assemblies are pretty expensive compared to standard cheap wheel bearings)?

Tires (all 4 identical (P215/70-R15 on Exploder alloy wheels) & same pressure, 35p.s.i.), bearings, brakes: All good. I still think it's staying at least partially in open loop mode, which is why I asked if it absolutely switches at 130 degrees F, or if it's a gradual lean out up to normal operating temp (195F in my case)? I see no reason for a rig with a 180 or 195 thermostat to run mid 140s in 90+ degree heat with A/C on unless something's amiss. Possibilities other than thermostat? Or am I confused? Wouldn't be the first time...

How did you determine the coolant temp is only in the 140s? I had a ford ranger that had a wire break to the O2 sensor and the mpg went from 21 to 13.

Low coolant temp

I checked with Infrared thermometer, 144 degrees F. Same with new stat.

Did you check the fan clutch?