I replaced the plugs in my wife's 850 with the Bosch platnum 4. A great inprovement over the original 3 electrode OEM. The reason was the OEM plugs were shot. I put the 4 electrode platnum plugs in my '92 240 wagon and there was no inprovement at all! The original VOLVO (Bosch) plugs looked pretty good. I think that you will save money with the copper core plugs and get identical performance...the 4 electrode platnum plugs will last a LOT longer. I found that the plugs in the 240 were VERY hard to remove because they had been in place so long ( I just bought the 240 last month). It may be a good idea to save money with the coper core plugs and change them out more often and reduce the risk of them siezing in place. The Porsche boys never apply anti sieze to the plugs because it can cause all sorts of problems with the electricty getting from the plug to ground. I never had a problem in many years using a little engine oil ( I usually let a drip drop on the new plug threads from the dipstick) but now I install them dry. Bosch will refund your money if you find the platnum 4 plugs give no improvement. They are banking on shadetree mechanics not wanting to do the job twice. I ordered the plugs from FCP and the price was right and they arrived next day- The problem was that 1 box contained the wrong plug!!!! Now I have to see what they will do about this. I had a tough time buying 1 plug on a Sunday afternoon. When I rode a Datsun 240 Z (in the stone age) it ran best with NGK. I was a big NGK fan till I bought a BMW and it preferred the Bosch. In marine applications the Motorcraft lasts longest. Nipondenso makes a quality cheap plug as well. If you want to be sure-use what came original.