I haven't pushed mine to the limit, yet! I trust it about as much as I trust a fuel gauge - if it says I need gas, I get gas! On the other hand, I have found this one to be quite accurate as far as updating the display depending on my current mpg - that's about all it can do, of course. It doesn't estimate what type of driving you'll be doing, and it can't predict the conditions in which you will be travelling, so trust it at your own risk (or amusement!).