I drive a '99 F-150 with the 4.6L and automatic. I've used Mobil 1 since 36,000 miles. I've done all maintenance as required. I had plugs installed at 100K.

I'm wondering if I should change coil packs or how do I tell? Any items that I might be doing extra I'd like to know about. Wheter it's engine, drivetrain, etc.

Another item. My truck seems to run as good as it ever has but the last time I checked my mileage it was at 19 per gallon. It has been as high as 20.5 per gallon when I first changed over to synthetic oil.

All suggestions will be appreciated.

Al in Tennessee

 

Im not sure about your decrease in gas milage, could be several things. Make sure that rear end is fluid filled and grease everything, and make sure you keep up your engine maintence up, and tranny fluid/filter every 30k or so and you should be good to go.