Engine Spark Plug Recommendations

guys on te turbo forums recomendthe ngk 5671a-9 which i would say is the heat range of a 3922?

3923 is the coldest plug in that size /range from Autolite, one reason I switched to the NGK

I replaced the spark plugs on a '006 GT that had 115,000 miles. (You can say it's almost 200k the way this one is driven!) The replacement plugs are Motorcraft platinum OEMs. And now for the serious part:

If the spark plugs have been in there for a while you should be aware that a good amount of oxidation has formed and it will interfere with their removal. (See below) This is the flaw in what seems like a good design. You don't have to gap these and they have more conductivity than regular plugs.



It's like a game of Operation (by Milton Bradley) except if you over-torque it you get a broken plug instead of a buzzer. Though you will still see a red light... be careful, Anger leads to the Dark Side. You see, the spark end is a porcelain segment inside of a metal sleeve which can break off where it connects to the plug's thread. So the upper half will exit leaving the bottom half unreachable. You will need a spark plug removal tool ($100 at Napa) - I tried everything else... EVERYTHING.


It comes with instructions but it's basically two tools in one. First mode will push the porcelain downward and out of the way. Second mode will create new threads on the inside of the metal sleeve so it can be torqued in reverse and pull the sleeve out of the hole. Squint your eyes for this next photo.


For first-timers: the distributor fits easily over the plug once the plug has been installed. The fastened distributor will keep the connection tight. Don't go listening for a Tupperware pop when you're replacing (reinstalling) the distributors over the plugs. Some recommend a gel to reduce condensation in there but gels are icky... you choose, I gave you Free Will.


Ownership of the tool will make you king among men... well, among late-model Mustang owners anyways.

PS: Most Mustangs I've come across seem to go 100,000 miles or more problem free with one or two owners. So suck it, Toyota. I hope this helps!