I finally got around to seeing what kind of fuel mileage my 2000 4.2 gets, and it came out to 12.5 mpg!! I drive primarily in the city, but is this normal? It seems extremely low and I drive like a little old grandma in the thing. Also, i'm pretty sure i noticed a decrease in fuel economy as soon as i had the egr purge valve replaced. that's when the fuel mileage seemed to absolutely go down the tube.
thanks,
mike

 

Around town my 05 4.2 does 15 mpg.

 

Thats about normal, maybe slightly low, check your tire pressures, you may be running a little rich also.

 

My tank is 21 gallons. I consistently get between 295-305 to a tank. This is whether I drive all freeway, all city, hard, grandma style..whatever..This calculates to roughly 14.28 miles to the gallon @ 300 miles. I am due for a full tuneup soon. I replaced the air filter and did a techron douche through the fuel system/intake but need to do plugs/wires/fuel filter(s) etc. Damn V8's....Love the power but S***..14 mpg kinda sucks!! sSo, 12.5 seems a bit low...

 

You could try cleaning the Mass Air. CRC just came out with a cleaner specially for this. I did mine and my mileage went up 20%. Was the best $6 I spent!