I have a 1994 940 non-turbo that I've had about one year. I am changing the current AutoLite spark plugs (unknown installation date) and going with NGK copper spark plugs, after reading the advice from so many on Brickboard to go with them.

I will post soon about any performance change.

But based on NGK's comments below, is there TRULY any difference in performance (not durabillity) between the coppers and platinums? I'm not a mechanic or expert, just wondering what the reality is.

Copied from a PDF at NGK website: "Almost all spark plugs use a copper core center to conduct the elecricity, jump the gap, and promote heat dissipation. All NGK spark plugs, including precious metal Iridium and Platinum, have a copper core.

When one talks in terms of nickel alloys, platinum and iridium, one is referring to its durability, or how long a spark plug will last before it needs to be replaced. However, when one talks about copper, he or she is referring to its ability to conduct electricity that is needed to fire across the gap and ignite the air/fuel mixture."
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'87 740GLE with 200K; '94 940 with 160K