Mileage drop in 2009 Prius

We purchased our brand new Prius in April, 2009. Our average mileage has consistently been 52-55 mpg. In the past month or so the mileage dropped to 50 mpg. After putting on snow tires it has dropped to 47-48 mpg. Have other people had similar drops in mileage? What have you done about it?

If you just put on snow tires I’ll assume you live in a cold weather part of the country. In cooler weather you’ll tend to run the heat more and the gas motor could be running more to provide the heat to the cabin. You could also live in an area where the gas is changed to a “winter” blend of oxygenated gas, which will reduce your mpg.

Finally the snow tires have a more open tread design, deeper tread, and greater rolling resistance than the tires on the car as it came from the factory. Toyota selects tires for the Prius which have low rolling resistance to enhance fuel economy.

Considering the cooler weather and less fuel efficient tires your mpg is still very good. My '03 Civic has the same kind of mpg drop when I put on the snows and drive in the winter. What you are experiencing is normal, you are just noticing it as you are focusing on tracking your mpg. Most cars get less mpg in cold weather, its just that the driver’s don’t notice the difference.

Thank you for your response. I had a feeling it was weather and snow tire related, but you confirmed in a way that makes sense.