The temperature in the Washington DC Area has dropped down to a high of 40 F degrees to a low of 28 F degrees. Fuel efficiency on my 2010 Toyota Prius III droped down to an average of 55 mpg for a oneway 12 mile commute
- this is down from an average of 65 mpg for the same
12 mile commute during the summer time. The problem is not with the tire's rolling resistance (tire pressures is
44 psi in front and 42 psi in the rear) but with the lower power performance from both the ICE and MG during the colder temperatures. Also using the defroster/heater during the winter lowers the ICE energy efficiency. Furthermore, It takes more energy for the ICE to keep the emissions control equipment at the proper temperature when the outside temperature is near freezing. To help keep the ICE warm - I've started to block both the top and bottom grills - during the 12 mile commute. I am monitoring the coolant temperatures via ScangaugeII via the FWT gauge. The ICE water/coolant temperature is peakomg somewhere between 160 F to 188 F degrees ( If the ScangaugeII FWT climbs to 200 F degrees I plan start removing the top grill blocking ) so far there has been no hint that the ICE might overheat due to the grill blocking. I've notice that grill blocking has reduce the number of time the ICE needs to run inorder to keep the ICE/emission temperature up...
2010 Prius III, Blue Ribbon/Dark Grey,OEM floormats Yokohama Avid S33 (44psi front, 42psi rear)