Toyota's Vice President of communications Irv Miller has published a post on the company blog refuting a recent report that the small fleet of plug-in Priuses is averaging 65 mpg
. The small group of converted PHEV Priuses that currently exist in the U.S. are mostly being used for demonstration purposes at auto shows and other events. A few of the cars are being used in university studies including one at University of California-Davis
. The current cars all use doubled up nickel metal hydride batteries rather than the lithium ion units that will go into the larger test fleet of 2010 Priuses coming late this year. Miller acknowledges that mileage data is being recorded from the demonstration cars but the results vary too much to be statistically significant. The mileage results of plug-in hybrids are highly dependent on driving cycles and styles. If the driving is kept within the plug-in charge range, the mileage is substantially higher than what can be expected after the charge is depleted. Any meaningful comparisons will require defining some representative test cycles.