Hello all,

I've got a 97 Supercab 4.6l with the manual 5 speed. I got it used a few years ago and was quite disappointed with the gas mileage (around 12 - 14 mpg) so I took it in for a tune-up. After paying about $300, I was told to be happy because these trucks don't get very good mpg.

I haven't been very happy with this truck as it has not had much torque, now gets around 10 mpg in the city and has a hard time going up a few hills here in the city (e.g. have to shift to first or second just to make it to the top).

Today, i pulled a plug and found the shop has put in Autolite APP794's versus the APP104 specified in the parts book. The difference appears to be that the APP104 has a longer threaded area and should probably sit deeper in the spark plug hole.

Does anybody know if this might be the cause of my poor mileage and lack of power?

 

i would change to the proper plugs. if the right plug extends further into the combustion chamber, that could well indeed be the source of your poor mileage and power. you may be getting incomplete burn of your fuel charge.

 

I agree, you should put the correct plugs in. I am suprised about the low gas mileage though. My F-250 4x4 with the auto gets around 14 in town, and 18 on the interstate regularly. I know every truck is different, but 10 seems awful low. Maybe the new plugs might gain you a few mpg's.

 

If it wasn't too long ago I would go back to that hack shop and have them install the correct plugs. Usually they keep receipts or maybe on your receipt(if you still have it) it will list the plugs installed.