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Message: <blockquote data-quote="525iBoy" data-source="post: 139812" data-attributes="member: 1183">IMHO, not complety true I tried the bosch platinum v.s. the bosch super, imperceptible difference  - even with diff heat ratings.  I'v also compared teh std NGKs and not much diff.But I've felt a sizable diff with the Bosch +4, and Bosch Platinum +4s.and while one does not need to change plugs every year.  (plugs can last for several years) it does make a diff in how the eng perf.  I used to smog/test my car emission and no doubt with a yearly sparkplug change the car runs cleaner.  Cleaning the plug helps but only marginally as the resistance of the insulator and conductors somehow detrioriate enough(I'm not sure how) to affect perf.  FActory reccommends change about every 2 years but its well known they like to stretch serv intervals for mktg purporses.</blockquote>