i have a 1999 F-150 4.6 and although the maintenance schedule states 100 thousand miles before spark plug change i have 55 thousand miles now and its running great my question is should i really wait that long to change the plugs and what is the best brand to put in this engine.....thanks

 

You're going to get alot of different opinions on when the change them, so basically I would say change them whenever you feel like it (you can wait until 100k or do it sooner, its just up to you really).

For brand just stick with Motorcraft or Autolite plugs.

 

I pulled the plugs out of my 97 4.6L at 56,000 miles. The electrodes were in pretty good shape and would have probably lasted for 100,000 miles. But, the exterior of the plugs are not platinum plated and they were severely corroded. I had a really hard time getting two of the plugs out since there was almost nothing left for the socket to grab onto.

While they're not too popular here, I put in some $2 Bosch Platinums after talking with some guys at work that race Fords. No complaints about their performance here.

 

HI!... I change my plugs once a season no matter what the milage. I use NGK TR-6's.