I wouldn't think the brand of spark plugs would make a drop of 3 MPG but you have a lot more experience in that than I do so I'll take your word for it. As far as using Motorcraft spark plugs, my truck will never see another one after the time and expense I incurred in changing the OE plugs. By the time I bought replacement plugs, extraction tools I had close to two hundred bucks in a spark plug change which I think is unacceptable. I know alot of people swear by using OEM parts and I would agree in most applications but I just can't get myself to do it with the plugs in this case. Thank you for your input.