I have a 2014 GMC 4 door I live in the county . I get about 18.5 driving to town and around town. I took my first road trip my screen said 18.9 at 77 . on my trip I filled up 4 times and I 17.3 ,18.6,18.7 and 21 on the last leg home 2 lane roads at 60 I check my mileage using a calculator and my indicator on the truck is .4-.7 tenths more then actual My lifetime on the remote link says 17 mpg I would suspect it to be off by .4-.7 mpg as I get by manual calculations Norm