Well I just did a round trip from NY to NC and my gauge was off by .3 in 1600 miles. I'd say that's pretty good...No they don't, that's the thing. TFL has a long term rebel, and the gauge is always quite optimistic compared to their hand calcs. And any gauge showing 30 MPG, average, in a heavy 2019 gas Ram is going to be "off", I'm sorry, it just is.