Without knowing all the variables, the numbers are really meaningless. You could have easily had a general downhill slope on your trip, or a tail wind. So don't read into them too much, Mario. Each individual user, and to a lesser extent each individual car, will have their own unique set of challenges that can greatly impact fuel economy.
I've gotten 92.4MPG in the 400,000 mile car over a 400 mile trip through the mountains of Colorado.
...At an average speed of 48MPH.