I had a 2018 34 ft Holiday Rambler that I towed a 2015 Cadillac SRX with. I added the 5 Star tune and it made the V-10 "wake up" and seemed to acclerate and shift better. Never saw any fuel mileage increase, but liked driving the rig more so probably used the acclerator pedal more? Was going to sell the rig so removed the 5 Star and had forgot how dull it was without. Ended up selling to a relative so put the 5 Star back in and showed the new buyer the difference, he said LEAVE IT hooked up!! No comparrison in with and without.