60K miles, actually.

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Ford backed off from their 100,00 mile recommendation for the 2004-2008 due to the breakage problem, but the plugs do fine till 100,000 in most cases. On the second set, I would not hesitate to go 100,000 before changing as long as I used the hi temp antisieze.

On my 5.0, they went back to the 100,000 recommendation. I have 73,000 plus right now and still runs as smooth as the day I bought it.

 

I still disagree. I've changed plugs in many of these trucks and by 80K miles the ground straps are showing significant erosion and the gaps have opened up considerably. My father's truck showed this at less than 60K miles. 60K is the best time to change them to maintain best performance and economy.

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That's fine but I have maintained mpg records on a spread sheet and have seen no reduction in mileage (other than when I changed tires). As long as it keeps running as it should and I don't get a loss of mpg, I'll go close to the 100,000. That should be in about 10 months on this truck.

On my 2005, I got nervous and changed them at 65,000 with none breaking. The plugs I removed look almost new, tips were still excellent.

I think a big contributor is using fuel with a good cleaner. I use Shell, Chevron and occasionally Texaco.