Over the course of the last 6 or so years and 120k miles, I have changed my Spark plugs a total of 7 times, every 20k miles on average. A Few months back I had 1 coil go bad in my truck, and while trying to figure out WHY my truck was idling bad and around 55-60 mph my truck was sputtering and rattling with horrid noises going on under the hood. I changed the Spark Plugs, Air Filter, PCV Valve System, Oil, Spark Plug wires, and every thing else before I broke down and took it into my Mums Mechanic. It turned out to be the Coil Pack... At the time, I wasent all that interested in looking up linecodes/product numbers on Automotive stores websites, and so I went into Autozone and got spark plugs (Autolite Double Platinum). The clerk there told me that they burn hotter which = better MPG gas wise, and are the best on the market. Up until this point, my truck always used Motorcraft Platinum and/or Bosch Platinum Plugs all swapped by a mechanic and all cheaper than these Autolites, so I was all like "What the hey, They seem to be better Plugs!" So after tinkering with the plugs, I switched them out myself, still didnt work, regardless, after the Coil pack change my truck still didnt seem to be itself, but I lived with it for 6000 miles, before today, while changing my oil, I decided to change the plugs too. The girlfriend is into Rally Car racing and in her Focus she put NGK Spark Plugs, thats where I heard of these certain plugs. Anyway, My truck now has the touch of it being new, a helluva lot touchier gas pedal, and my gas Mileage has jumped 2mpg, between that and going to a 5w30 from a 10w30. It runs roughly as it did when the Bosch plugs were in there, and better than the OEM Motorcraft ones and A LOT better than the autolites. I might get some [censored] from this, but like Fram Oil Filters, Autolite plugs, owned by the same company, are overpriced and not worth their extra cost, I am just talking about my experience, some of your cars may run good on Autolite plugs, but everyone out there thinking or needing to change their plugs soon, try the NGK Lineup, AAP or AZ may tell you that theyre for "Imports Only" but snap back at them and say "What car these days ISNT Imported?" I took the product number in there, and they sold em to me. I will follow up every 5000 miles as I will check the plugs with each oil change, the condition of the plugs ETC. I paid 1.99 a plug, for V-Power Plugs, a better plug both performence wise and build wise to me versus the 5 dollar and change Autolite D Platinum!