Mileage Question

I recently had a front to rear maintenance done to my 94 - 4.3 with 80K miles. Plugs, wires, hoses, anti-freeze, belt, trans fluid, diff fluid, water pump and thermostat. Since this work was done my gas mileage has dropped on Highway from 26 to 20 and in city from 21 to 17. The only change in driving I can see is the temperature is much cooler than before. I know the thermostat is a lower setting now. Can this cause the mileage drop or should I be looking some ware else?

Good question, I replaced my stock 195 with a 180 and also noticed a drop in mileage. Not as much as yours though. You might need to get your computer reprogrammed for your new temp.

It might be beacause the cooler temperature could be causing the Computer to keep running the engine richer than normal to help warm it up to it's set temperature of 195 Degrees.

id recommend putting the original temperature thermostat back on.
a lot of people put on different thermostats thinkin that it will help them in some way.
it wont.
it usually just causes more problems than it fixes.