How often should I replace my plugs? I'm at about 28k now
Ford shipped all the LS motors with their Motorcraft Platinum plugs with the 100k mile "tune-up interval".
Myself, I've been changing the Motorcraft Platinums out for Bosch Platinum IR Fusion at about 50k miles and each of my FLM vehicles have seen a notable improvment in economy, response, and overall power. Keep in mind these ARE just spark plugs, it's not like pulling a Quik and installing a S/C, but the changes are noticable.
I've noticed that once the stock Motorcraft reach about 40k miles, the wear on the ground electrode becomes slightly/visablly uneven (the ground electrode IS the "wear item" of a spark plug). I believe this uneven wear to be the point when power and economy start dwindling slightly. It takes another 10-20k miles so the change to the new plugs is really noteworthy.
The Bosch Plat IR Fusions have four grounding electrodes versus the single one the Motorcaft Plats are equipped with. With the ground electrodes being the the part of the spark plug that wears, four has gotta be better than one, right?
The iridium plugs are nice because the plug reaches it's self cleaning temp hundreds of percent faster than a standard platinum. Reaching the self cleaning temp faster means they are harder to foul out and therefore they last longer than what the manufacturers advertise as 100,000 miles between tuneups, so popping in a set of iriduims should have life beyond what the car ever would.
