I read the specifications of the navman Fuel 3100 and am confused. The specs say that the accuracy is .1 of a unit up to 999 units and then 1 unit up to 9999 units. My vessel gets approximately .6 mpg at cruise. If the navman unit displays this as 0.6 mpg then it will not be very useful in finding the maximum economy. IF on the other hand it is displayed as 0.64, then by watching the "4", that is, the hundtreths value, I can easily find the best economy. I doubt that I will improve to .7 mpg ( a 16% increase) thus the unit will not show a change. However if I improve from .60 to .64 ( a 4.8%improvemet) the unit, if it reads to the hundredths value, can help. Any information would be appreciated. The Navman web site has not answered this question (nor have Navman personnel).