Is there kind of a rule of thumb when you see the Trip Summary showing a particular MPG and what you are actually getting? My wife just took our brand new 2013 on a 300 mile trip, 65mph into a head wind all the way, and the Trip Summary showed 49mpg and after fill up and doing the math, it was closer to 42. Of course I don't know how full she got it. Thanks.....I'm sure something like this gets asked all the time. We have had the new Prius now for 4 days and I only got to drive it on the first day.....bummer.
Many threads here about any where from a 5 to 7% difference from the MFD and actual mpg's. While your difference is 15%, it maybe issues in the first tank or two differences. In time I think you will find that you might average a 7% difference as I do over time....
Never try and calculate a first "full" tank from the dealer. It is rarely ever completely full. Also never try and calculate from the Trip Summary screen on the 2012+ Prius. Use the Trip A or B information assuming you reset it at your last fill up.
