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Old 10-21-2015, 06:34 AM   #28 (permalink)
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Join Date: Feb 2010
Location: CA
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Sorry to revive a dead thread but I purchased both the standard copper plugs and the Iridium plugs (both NGK brand) to test for a difference in mpg. So far, my scan gauge is telling me that I yielded a 4-10% increase in mpg with the copper plugs along my normal commute with no traffic, similar weather, and the same pulse and glide tactic. Further testing is required as I have not yet refilled the tank yet and can only go with what the scangauge is telling me. Will update this post in the coming weeks/months.

I drive a 2007 Toyota Yaris Hatchback by the way.
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