Yes what is gas milage haha I get fun per gallon..... and alot of it!

But seriously these are lock up style converters, which will drive like stock, they are not comparable to say a 4500 stall that will slip if your under 3000 rpm, as far as milage goes I dont see how they could decrease unless you drive the ca harder from stop lights, they, and most converters work better by not trying to foot brake at say 2500 and launch. you want to hold the revs up high enough not to bog but low enough not to engage the converter, say 1000rpm ish and snap the throttle.