More from bobistheoilguy:
"Here is my thinking how people sometimes get better gas mileage by adding bogus things to vehicals that claim to increase fuel mileage. They instantly change their driving habits. They are driving more conservatively after adding such devices, and contribute the increase in mileage to the product. "
Your improved gas mileage most likely came from from other factors. Been there and done that.
negative. I am always concious of my mileage and my driving habbits. I am annal about it. You won't find a V8 Explorer getting 20 mpg driving like I am doing....it's just not gonna happen.....but it is safe to be skeptical