Spark Plugs

If you have not done any research, you might jump to the conclusion that the best spark plugs for your 928 would be Bosch, and that the best Bosch plugs would be the platinum or the multi-electrode ones.

Wrong.

The best Bosch plugs would be the standard copper version. The 928 does not like the platinum or multi-electrode versions.

My wife's Cadillac STS with the Northstar all-aluminum, quad-cam V-8 started running very poorly. I removed the Bosch Platinums that I installed about 20,000 miles ago, and installed ACDelco Platinum Pro plugs. Problem solved. I did absolutely nothing else, and the engine now runs strongly and smoothly. GM engines don't like the Bosch platinums either...

I had the same experience in my early days of 928 ownership with Platinum 4 prong plugs.
Wally is right as always - stick with the plugs that Porsche put in the cars from the factory or their direct equivalent - nothing else.

Good advice....sometimes what seems logical, is not always! I tend to lean towards Porsche engineers knowing what they are doing (did

I dont remember what I put in it but I wonder if it was the bosch

Bosch is fine as long as it is the correct plug. Rule of thumb ----
WR8DC+ - Copper - 77 to 80
WR8DS - 80 to 84
WR7DC+ - Copper was 999 170 119 90 - 83 to 91
WR7 DTC 92 to 95 (alternative is NGK BP6ET)

That is some good info there! Thanks Rog!