I found this rather interesting... http://avt.inel.gov/hev.html A summary of the data, all accumulated in Arizona, consists of the following: 6 Insights (5 CVT, 1 Manual) driven 347,000 miles resulted in 46.0 MPG 4 Civic-Hybrids (all CVT) driven 284,000 miles resulted in an average of 38.0 MPG 4 Classic Prius driven 380,000 miles resulted in an average of 41.1 MPG 2 (not completely broken-in yet, so MPG will be even better later) 2004 Prius driven 16,000 miles resulting in an average of 44.6 MPG
that jives pretty well with my real world mileage, and considering the difference in useability between the insight and the prius, it's quite acceptable
Maybe that downward spike there is a cold snap in February? I would suspect the slope as a whole would be from decreasing winter temperatures, as well...