The specs call for a Champion J4J or equivalent. I understand these have been replaced by a J4C. When I replaced the plugs last time, my local Napa auto parts man told me they had been superseded by the J6C, which are what I bought. When I checked my plugs this Spring, they were pretty fouled (black & slightly wet). I'm going to replace them, but I'm not sure which to use. I'm inclined to look for some J4Cs right now. What's the difference in the heat range between the two. Is the J6C a cooler plug? Thanks.
