Does as Advertised
It calibrated my speedometer since I put larger tires on. It takes trial and error. Just because you put 35" tires on doesn't mean you just set this to 35". You have to test it. I have 34" tires. Had to set this thing to 32.5" for the speedo to be accurate. Unfortunately, this is my only option at this time since the tuners are unable to calibrate the 2015 F-150 at this time. Dealership wanted the same price as this calibrator for a one time change. Good product.
Couldn't really tell any difference on 87 octane but it did seem to come alive a bit on 93. Throttle response is definitely quicker though. I'd probably buy again just because I've heard bad things about the more expensive units on the market. Don't really think it helps gas mileage either. I do however have a CAI on the way & put exhaust on last month so we'll see how all the mods work together.