I measure first bar on 5 min consumption bar. If it's at 10 l/100km => cold night, poor result. If 7.5 l/100km => night about 8 degrees, there is a chance for good normal mode result with low heater penalty. If about 5.5 l/100km => car is hot (at least +15 deg outside or short break after previous trip) => big chance for 4.7 l/100km for the rest of the trip. Now I understand why both Auris and Yaris in user's manual had section "Starting vehicle" split between Germany and other countries. After reading it 3 times I found the difference. In DE - start engine and begin travel immediately. In other countries - start engine, wait for 10 seconds, begin travel. No startup split found in Prius manual.