Autolite APP104
I received these plugs from two different vendors; 2 of the left plug, 4 of the right. Both labeled Autolite APP104.
The little electrodes are different, but I don't know how much difference that makes in the engine (3.0L in a '93 XLT)
Would you use this combination of designs?

 

Nope... never mix plugs, if you have a modern vehicle with a ECM/PCM. My son recently got new plugs for his Honda Fit. The old set had one pointed electrode, and one flat-faced one. The new ones have both sharply-pointed. ONE of the plugs in that engine is hard to get to without about two u-joints and a lot of fiddling. So he thought to leave the old one in (????).

I set them up on our bench with a spark coil and watched the spark profile and rise-time in peak voltage on each with a high-voltage probe and a recording oscilloscope. The peak rose later and FAR higher before striking on the one with the blunt electrode, and the spark was actually thinner and sort of 'spread out' in strands, rather than fat and hot. The one with the pointed electrodes made a fat, wide spark.

The PCM can sense the delay in firing due to the necessary rise time in voltage in one over the other, and adjust. But if they're mixed, it can't reach an optimum setting.

Lloyd

 

Change of heart: my nearby AutoZone has these plugs; I'm going to take the hit and buy a couple of them (same $ as I paid for 4 on Amaz). That's provided AutoZone is selling the new style. That will eliminate any question.

(I finally got Autolite tech support on the phone and the agent knew exactly what I was trying to describe.

He assures me that, for all practical purposes, the two are identical and I can mix them in an engine, no prob.

The left plug is an older style, the right one newer, but they fire exactly the same, same heat range, spark, etc., etc., so I'm going with these.)

 

Good luck!

 

In that engine? You won't feel a bit of difference from a "complete set" compared to what is in the picture. It doesn't work hard enough to even matter. They are tuned down, which is why that engine lasts so long.