What range of MPG should I expect from the 4.9L 6cyl. engine?

 

When I bought my 95 I got around 14 mpg with no load. After changing the air temperature sensor, the throttle position sensor, changed the o2 sensor, put a restrictor plate on the egr, added an electric fan, put in a new ignition module, a 50kv coil, new cap and rotor, side gapped champion truck plugs,new plug wires (motorcraft) a gibson high flow exhaust, cleaned the throttle body, K&N drop in filter with a modified box, I now get 17-21 mpg during the summer depending on the wind.
That was a lot to do, but the end result was well worth it as I drive 90 miles round trip every day to work.

The truck has 82,000 miles on it.

 

My '92 2WD SCab with Auto and 3.55's averaged about 15 mpg.