My 95 F150 5.8L has always netted me about 9mpg in the 5 years I've owned her. Threw in a can of RP fuel treatment last week and that jumped to 11mpg for that tank of gas that lasted 200mi instead of 170ish. So impressed was I that I treated the next tank of gas with another can of RP, but strangely, I am back to my 9mpg/170 range for that tank every subsequent tank since. Driving patterns and weather conditions were no different on the initial treatment.