Has anyone ever tried the fuel additive "CA40?"?

i used it to drive a 16 ft penske truck 720 miles. they estimated that i would get 6 - 9 miles per gallon. i got 10.4 miles per gallon. i did find i got better gas mileage when i used the ca40 when the tank was on empty. it seemed to mix better. i was just wondering what other people thought of the product.