1. Driving in the rain consume 20% additional (I'm hoping that is not just windshield wipers)
Bjørn Nyland has discussed this on his You Tube channel. A wet road increases the rolling resistance of the tires.
There is a research paper (*) I found online with real data. A few quotes:
"At 80 km/h, 0.65-mm thick water film increases rolling resistance by over 50%,"
"The increase of rolling resistance is higher for higher speeds"
"Water film thickness has a considerable influence on rolling resistance increase"
"At low speeds (30 km/h), even very thin water film has considerable impact on rolling resistance."
* "Influence of Road Wetness on Tire-Pavement Rolling Resistance" Journal of Civil Engineering and Architecture 9 (2015)