First spark plug replacement?
The problem with service intervals.... is ALL the manufacturers are trying to say their vehicle is cheap to service/requires little service etc. It's a bragging/selling point.
I'd like to think the informed/educated consumer takes a good share of these service intervals with a grain of salt starting with our so called IOLM's.
10K oil change intervals.
Lifetime trans fluid
100K plugs
The list is as long as the service schedule. Keeping your truck three years? Most likely no worries. Making the vehicle last as long as possible? Most maintenance would be better served doing more often.
With only 25K on the truck at almost four years I haven't changed the plugs on my 3.5TT eco but will pull then at 30K for inspection and change if needed. Already have the plugs sitting here.
I'd like to think the informed/educated consumer takes a good share of these service intervals with a grain of salt starting with our so called IOLM's.
10K oil change intervals.
Lifetime trans fluid
100K plugs
The list is as long as the service schedule. Keeping your truck three years? Most likely no worries. Making the vehicle last as long as possible? Most maintenance would be better served doing more often.
With only 25K on the truck at almost four years I haven't changed the plugs on my 3.5TT eco but will pull then at 30K for inspection and change if needed. Already have the plugs sitting here.
5 Year Member
Joined: Mar 2016
Posts: 560
Likes: 143
From: Newnan, GA
I changed my '18 5.0 plugs at 6500 mi. Overkill, right? Well, the truck had a dirty fuel system from the day I got it new off the lot. Figure it was water in the tank from sitting in cold winter weather with the factory fill few gals in tank. Was having random misfires according to Torque Pro app. Ran a can of BK fuel system cleaner through tank and a couple tanks of gas before I changed them. Truck runs much smoother now. Plugs are cheap and the job on the 5.0 is MUCH easier than my old 5.4.
Thread Starter
Senior Member
Joined: Dec 2016
Posts: 337
Likes: 51
So got the truck back today after the plugs were done as well as fixing the crank case pressure irregularity again, again....
With the new plugs the really rough idle that it's had since I purchased it with 20,000 miles is completely gone. I am quite impressed.
With the new plugs the really rough idle that it's had since I purchased it with 20,000 miles is completely gone. I am quite impressed.
5 Year Member
Joined: May 2013
Posts: 1,251
Likes: 263
From: San Antonio, Texas
Regardless of the engine nd type of plug I've always done plug changes between 25-30k miles. Cheap insurance. However, if the plugs are a giant hassle to get to I might let them go to 50k.
Senior Member
Joined: Sep 2010
Posts: 368
Likes: 43
From: Vermont
+2 for the Motorcraft. It's the SP-534 for the 3.5 eco. I believe it's an updated plug as well. The one's I got came pre-gapped (0.35", IIRC).
Last edited by Fatmattyd; Jan 26, 2019 at 02:24 PM. Reason: Corrected plug gap spec
