OK, before I pulled the old ones out I gapped the new ones at .054 like they're supposed to be. When I pulled out the 3 passenger side, I could tell that whoever put them in.... FORD.... never gapped them. All 3 of them were almost .070! There wasn't enough were on the electrodes to compensate for the distance so that's not what it was. The didn't take the time to gap the plugs before they installed them. The 3 on the driver's side were a little better but even with normal wear and tear you can tell that they probably were not gapped when installed. Since the truck only has 60k miles on it and they were motorocraft I feel fairly certain that they air the original plugs. I have been getting 12-13 mpg city and hwy since I bought it back in October. Could this be the cause? Last month I changed the fuel filter. This weekend I changed the sparkplugs, pcv valve and air filter. What are your thoughts as to the spark plug gap/milage issue? Is there one? I would think that I should at least get 15 mpg out of this thing in the city. Curious... what's the gap supposed to be for the 3.8?

 

I get 18.4 average, I would certainly think that those plugs were hogging some of your power and fuel economy.

 

But that much difference, I just can't see in the plugs alone, but id defiantly wasn't running to cold a spark.....But then I never owned a 3.8...

 

I may have confused you with the last thing I said. My truck is a 2000 so I actually have a 4.2 - I was just curious what the gap was supposed to be on the 3.8. All I know is that it does seem to run MUCH smoother. That could be from everything that got changed this weekend but we'll see.