Both routinely get 45mpg in mixed rolling hills and flat terraine. 35mpg around town, which is all up and down. Mileage declines in the winter to 39mpg.
35 mpg = 6.7L/100km; 45 = 5.22L/100km. I can get >30mpg in the summer in my parents' RX400h, but they struggle to even get 20mpg in the winter. Yes, cold weather affects hybrids.
Your choice of wording makes me wonder if you're comparing your own use of the RX to your parents' use of it. Your driving may include typically longer trips and perhaps more summer driving and less winter driving.
The Escape Hybrid goes from typically 40mpg in the summer to more like 36-37 in winter doing the same drives. Nowhere near the difference you're seeing.
On one hand, winters are mild here, but on the other hand winter mileage is also reduced by wet/snowy roads, lower tire pressure, less efficient snow tires, more hvac use and less energy in the gas. So the residual temperature effects on the powertrain must be almost trivial.
