A Note About Winter Temperature Readings and the Mileage Log:

Before the Prius can turn off the engine to begin saving fuel, it must ensure that the engine and emission system are operating at the proper temperature to produce SULEV (Super Ultra Low Emission Vehicle) level emissions from the tailpipe. In the winter (especially here in MN) this can result in substantially less driving in the Prius' electric only "stealth" mode, as well as a noticeable drop in gas mileage. Over the past few years, I've just accepted this as a fact of life for my Prius, which is kept outside year-round. However, I've occasionally read about people who have blocked the lower front grille of their Prius during the winter to provide added insulation for the engine compartment, which helps the car warm-up faster and maintain the optimal engine temperature for a longer period of time.

After reading this message on the Yahoo! Prius forum by a fellow Minnesotan, I decided to try his method of blocking the grille to see if it makes a noticeable improvement in my mileage this winter. However, since the Prius' outside temperature sensor is located behind the newly covered grille, the temperature readings on the Prius' multi-display will likely be considerably higher than the actual outside air temperature. 

In order to ensure reasonable data for my winter mileage log, I will make an attempt to record both the temperature displayed on the screen and an official temperature reading from a TV weather station (or equivalent) whenever I fill the gas tank. I will enter the temperature readings into the mileage log in the format Prius reading / TV reading. If I am not able to find a reasonable reading from the TV or internet, only the Prius' reading will be posted. 

Ahh, the things people will do to in the name of science and data collection! ;-)