I've never taken a hit from snow tires being on the car, any car. The usual winter mpg "hit" is usually cased by warming up the vehicle on those cold mornings. Hybrids also take a hit in colder weather, although I've not experienced a huge hit. Last winter was the third season for our Camry Hybrid on General Alti Max snow tires, a fairly agressive tread. Gas mileage improved from the Bridgestone LRR tires that came with the car. But as the winter got colder, mileage declined. One thing that changed mileage for the better, was to start up in the driveway, and wait a minute or two, then leave. Gradually the mileage went higher by 1-2 mpg overall. With the snow tires still on, when the temps reached the 40's, mpg grew again, and got back to high levels as temps were in the 50's. Interestingly, when I put a set of the Yokahama Avid Envigors on the CH, mileage increased over the LRR tires. Those same tires look better after three years than the Bridgestone LRR's did new
