j_99GT

So this is my first time posting on a forum, I’ve been an avid reader when I need info but I’ve never actually asked the questions myself, figured it’d be a good time to get to it.

Some quick background, I’ve owned two V6 Mustangs (a 98 and an 02), and I’ve always replaced the plugs with OEM motocrafts. Now I’ve got a 99 GT and it’s time to replace the plugs, and I’m wondering if there’s any benefit to going with a higher performance plug instead of an OEM. The motor is stock except for the CAI and I won’t be making any significant engine mods in the near future. Any suggestions?

Buck Sergeant

J 99GT, from what you outlined, unless you plan on bumping up the compression, I would stay with the OEM plugs. You could play a little bit with the gap, but again the benefits from "high performance," plugs will probably not even be noticed. I would tweek in the plug gap, and the timing.

imp

Good advice as far as I'm concerned......I bought a set of "Double Platinums", not sure exactly WTH that means, because there was a massive rebate going on, price came to, like, under a buck each. They go up from Platinum to Iridium, but these things were argued to death on another forum which has essentially driven me away. imp

Z28KLR

Stock equivalent platinums, or if you really like to party then go with copper. Only difference between the two is service life and technically speaking copper is a superior conductor. Set of Autolite 764's will run you about $8. Don't do iridium, or anything with multiple electrodes or anything else that promises more hp and/or mpg. It's all marketing bs, a spark is a spark.

imp

Right! And given that the resistance of plug wires are specified at very high resistance values compared to whatever metal the plug electrodes are made of, IMO the only real advantage of the exotic metals is less burn-away, rather than any effect on the spark itself.

Plug life is so high anyway, I just don't worry about it! imp

j_99GT

thanks for the suggestions. I ended up grabbing some motorcraft platinum 493s

Derf00

Double platinum just means both the cathode and ground strap have a platinum head on them. Regular or Single platinum usually just cap the cathode with platinum and leave the electrode bare or vice-versa.

Besides less burnaway on the plug firing surfaces like mentioned that same advantage with platinum and iridium lets manufacturers use a smaller surface area for the spark to be emitted from so, you end up with a more consistent and controlled spark and combustion pattern that lets the PCM more finely tune the A/F table across various loads. If you were to reduce the spark surfaces with regular plugs you'd burn through them much faster than 20-30k miles.

Is the more controlled and consistent spark noticeable in the real world? Probably not but, with all the hype about "No maintenance required for umpteen miles" and MPG requirements only going up, every bit counts.

Also, a lot of OEM's take into account plug resistance when designing their ignition systems so the higher resistance plug is actually required in many cases. If you use plain copper plug or non-resistor type plugs or you can burn out the coils or worse, Damage the PCM.

The 05-06 Ford Escapes are a key example of this. Some cars got non-resistor plugs on the factory line. The lack of resistance reduced the amount of resistance (duh) in the circuit and also created feedback into the secondary coil of the Ignition coils. This popped the coil and also ended up popping the PCM ignition coil drivers. The only fix was replacing ALL the coils, the PCM and plugs with the proper resistor style plug. An expensive fix even if you go the DIY route. ($600-800)(Ford wanted over $2800!). Ford ended up putting out a TSB for it but of course that just provides a how-to for fixing the issue.

WhiteFoxGT

dont miss diagnosing those when i worked at ford... saw DOZENS of escapes needing PCMs lol

go with some ngk tr55 or whatever the autolite OE equivalents are.

Derf00

I bet! I see them all the time on the Escape forum i'm on.
The cost from a dealer is just crushing! It's still hard to swallow as a DIYer at $600 to $800 in parts alone!

imp

Amazing information about factory screw-up! Thanks to you all.