2011 Ecoboost 3.5, 66000 miles. I get a little mis-fire when I stomp on it. So, maybe I'm past the spark plug change interval. Wondering if I'm late, or is it 100,000?
Great truck, runs fine.

 

You can see read your manual at owner.ford.com.

Yes, it's 100,000 miles.

 

I would change them now, 100,000 is a little too far in my opinion

 

Change them out; I know Ford recommends replacing them every 100k miles but that's too long imo. I change mine once a year or approximately every 15,000 miles on my 2014 EcoBoost.

 

That's a bit crazy.

 

I changed the ones in my 2016 3.5 eco 68,000 miles.
The actual mechanics suggest 50-60,000 miles. It might be okay to go 100,000 like the manual says, but the people who wrote the book aren't the same people that work on YOUR vehicle.
You can wait until 100,000 if you want to but there is no need to and there is nothing wrong with changing now. Unless you won't have the vehicle at 100,000 then you can let somebody else deal with it. I probably won't get 100,000 out of mine but I changed them anyway.

 

Even old copper core plugs can go way beyond that. I hope you don't change oil with every fuel fill up.

 

I would change them but I wouldn't be surprised if the misfire still occurs afterwards.

 

I believe that leaving ANY threaded fixture in place for 100k miles, usually 5 to 10 years, is asking for trouble. There will be an untold number of heat cycles and wet-dry cycles during that time. If the plugs were installed with a smear of Never-Seize that would be helpful but 100k miles is, in my opinion still too long.

Back in the day, I used to R&R once a year to inspect them for color and deposits as a measure of how the vehicle was running. I wouldn't do that with today's plugs but given normal use, I am guessing at no more than three years. That is what I am planning and I will use Never Seize.

 

1) The recommended interval, used to be in the owners manual...years ago. But thanks for the info.
2) Just trying to find out if I missed the change if it was required at 30K or 50K.
3) Yep, used to change out Dad's 66 Mustang every 12K along with the points and condenser too.
4) Could be that I'm using 87 Octane fuel. Just not sure.