I had 2 Coil Over Plugs (COP) that were replaced by a mechanic several months ago. It was Cop #1 and #6. Now it looks that #7 needs to be replaced. My mechanice suggested that i just replace all the spark plugs. Currently my Expedition has approximately 89,800 miles. Should I go with Motorcraft or is there an aftermarket brand that some of you prefer for better performance?
Thanks for replying. Yeah, I did some research here and looked at some older threads related to spark plugs. It looks like OEM is the way to go. In fact, I already had them replaced yesterday by a local mechanic. This guys knows his stuff. It took him 2 hours to complete the job. He only charged me $100 to replace them, inlcuding the #7 ignition coil that went bad. Let me tell you guys, this made a huge improvement, I feel as if I gained 20 horsepower by simply changing the plugs! I can't believe the engine just feels smoother at idle. My wife was suprised as well. It feels like a brand new car. I got the Motorcraft plugs at O'Reilly's for $7.99 each. If you guys are considering changing the plugs, definitely go with OEM.