Reviewed By christopher e (Fayetteville, NC) Reviewed for a 2011 GMC Sierra —8/11/2013 6:00 PM
I only gave the spark plugs 4 stars so far because I've noticed a 2 mpg increase for highway and a much faster response from V8 to V4, but strangely enough even with my light foot my city mpg has gone down by 1mpg. Weird right? The most important thing to know however is that you MUST WAIT FOR YOUR COMPUTER TO ADJUST TO THE NEW SPARK PLUGS LIKE THE INSTRUCTIONS SAY! Your engine may have a code for multiple misfires for the first 50-60 miles but it will fix itself. I have had them for 2 weeks.