MY 02 Impreza O2 Sensor

Don't know about the other stuff, but my mechanic (a Japanese car specialist) told me to stay far, far away from Bosch platinums. They used to use Bosch platinums, and they told me stories of finding the center electrodes eroded or broken off. They're made with a thin platinum wire buried flush at the end of the ceramic insulator. Bosch claims it gets hot and self-cleans, but without melting away. Real world evidence seems to be contrary.

They currently use Denso plugs, even though a lot of the makes they service only factory specify NGK.

Very unimpressed with the Bosch Platinum. The center electrode does indeed erode away into the porcelain, then the spark has to travel up the porcelain to get to the ground electrode. The set I tried wore away within 10 k km (6000 mi)or so, and the vehicle was harder to start and did not run like it normally should. When I put in regular plugs, the car started easier and ran better.

I have been using NGK platinums and am very satisfied. Will try their irridium plugs next time just to see.

This should have a picture:

Although this is the Platinum2, all of their platinum plugs have a center electrode flush with their insulator.

That's interesting as my experience with the Bosch platinum, single ground electrode, plug has been very favorable. I've had them in my 92 SVX for over 25k miles and although I haven't taken them out to examine electrode wear, they haven't caused any hint of misfire and the car starts quickly. I just came back from a 2000 mi. high speed road trip on which I averaged 26.5 mpg so the performance is obviously there as I'm sure I would have noticed any misfiring in reduced fuel economy.

The problem I alwys had with them is they foul within a week. Not a problem if your car doesn't burn any oil I guess. Regular plugs worked fine in the same motor so I stuck with those.

It's not that they always cause problems, but that there seems to be an inordinate rate of problems. Also, many of the problems reported with the Bosch platinums seem to happen in smaller, hotter running engines. If I recall, the SVX has a 6-cyl engine under the hood.

However - I still feel that sticking with factory plugs is the best way to go unless you've modified the engine, esp with an ignition system upgrade.