I have to go with the guys who are sold on the Bosch platinums. I have used them all on a vehicle I own that was real tough on plugs (an original Chevy S-10 4 banger that called for copper core AC plugs), and have had very good luck with them, when the copper core AC plugs would quit at about 10,000 miles. The rig was not driveable with brand new V-power plugs, whatever spark voltage waveform the HEI system delivered (the AMC/Renix 4.0 secondary side appears to be of similar design) would not fire those plugs under pressure, and the electrodes just melted off of the Champions. This was, of course, in a rig that had some peculiar issues (the all cast iron 2.0 engine should have been built with a heat shield between the exhaust and the plugs), but it turned me off of the NGKs and the Champions and I'll not likely buy them again for anything. I get a solid 50K out of the Platinums in whatever I put them in. The thin electrode encased in the isulator, as they are, is not a design that inspired a lot of confidence at first glance, but I think the full encasement serves to keep the electrode cool and preserve the correct resistance in the core, at the same time resisting widening of the gap over time.
