Well, with 1 tank in the books, I got maybe a fraction of a mpg better than usual, but, I think it's wise to look at this product over at least 3-4 tanks. It's just not enough data to make a call, yet. I can say without a shadow of a doubt, that my truck did not even approach the 20 mpg mark that Mr. Anonymous indicated he's had no problem achieving with the same exact vehicle. I'm beginning to wonder about old Mr. A...one of his posts sounded alot like a commercial for MK 100. Hmmm. I wonder if he'd trade me trucks for a month?