Review on NGK 3186 Spark Plug Replacement: Enhance Engine Performance with One Easy Fix by Jeff Rubio

I disagree with the opinion of several "experts" regarding the use of an NGK spark plug in a Chevy C-3500 Dually that had AC-Delco in the large 7.4-litre -Block Platinum. I was told there would be performance issues, outages, etc. Well I have none of it after almost 1000 miles and my engine sounds lighter at all rpm. I could drive 440 miles on a full tank. refueling took 33.5 gallons; this equates to 13.13 mpg. That's about 1.6mpg better than what I'm used to with a standard Delco AC plug. (I use 5w-20 Mobile-1 synthetic oil, that helps too) A word to the wise: don't take factory spacing for granted, get it set right before you install it. My car required .060", but these spark plugs came from the factory much smaller than that size. I did extensive research on NGK, AC Delco and Autolite spark plugs before deciding on NGK as it has the highest build quality, fit, finish and tolerances. Stick the Autolite and AC-Delco alongside the NGK, the difference is obvious and the Autolite will look like a piece of junk and the ACD looks a little better for putting an 'unknown' spark plug in my car. Update: Filled up on September 1, 2011 with 366 miles on the odometer and only used 26.8 gallons. This time I got 13.65 mpg. The only difference I can remember is that I used the cruise control several times more than in the past.