Just did a plug change on the Eco. 29,000 miles. No missing or rough idle or any symptoms to prompt it, other than hearing it was a good thing to do around 30k miles....

Replaced with the MC spec plugs of course. I got them from Amazon for something like $3/plug, so I got 2 sets of them.

So much easier to do than the 97 5.4 that's for sure!

Old plugs looked okay, but the gap was a tad more than .030. I checked the gaps on the new plugs and they were pretty close to .030 out of the box, but I needed to adjust each one just a tad.

Pretty straight forward, just like everyone says... It's actually easier to do than changing the oil! ha, ha

Mitch

 

Plug change at 29,000 miles? Whoever told you 30,000 miles is just messing with you.

 

Real world experiences are showing that useful plug life in a Ecoboost is 40k at best. You can probably run your NA 3.5 to 100k.

 

The plug life is very dependent on how you drive. Lots of high boost runs tends to beat up the plugs. Light throttle doesn't create near the cylinder pressure and they will last a lot longer.