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Message: <blockquote data-quote="adriver" data-source="post: 16780" data-attributes="member: 795">Old thread, butThe Iridium plug,  41-110 (with a .040 gap) was the originally installed plug when they started the NBS/Gen III LS.  I think it was in 2003, but at some point early on, they changed the plug to the platinum and it became the superseded part number.   The platinum plug 41-962 has a .060 gap.   I think I have only seen them come pre-gapped, but you can use either one.  The Iridiums will last about twice as long (100k miles vs ~60K miles) but also cost about twice as much.  SUPPOSEDLY the iridiums are two hairs better for performance, but if someone knows details why, they know more than I do about em.  I think it has to do with the shorter gap having a "more responsive spark".  I felt an improvement when I installed iridiums, but that could obviously be from just putting in new plugs so it's not really fair to mention.   My guess is GM  only did it, (downgraded) to save a few bucks.In the 02 owner's manual it has the replacement plug listed as NGK PZTR5A15 (iridium)<a href="https://www.sparkplug-crossreference.com/convert/NGK_PN/PZTR5A-15" target="_blank">NGK PZTR5A-15 - Cross Reference | sparkplug-crossreference.com</a>(The GM part number for 4.8/5.3 is PTJ14R15.   For the 6.0 it is PTZ16R15, yet both have the same NGK plug number).</blockquote>