It does affect some, BTU 129 500 vs 110 075
Aerodynamic & rolling resistance, power & MPG calculator - EcoModder.com, in practice I have no hope to go under 5l/100km with winter stuff but with summer stuff I can manage to 4.8l/100km if weather is nice. This even at winter air is cooler so more oxygen to cylinders. Same tires and pretty much same everything else, however two winters ago it was that I noticed that. Last winter was real disaster in fuel economy wise for me.