To answer your question though winter blend does not get as good gas mileage as a summer blend gas. And also in cold weather because your car takes longer to warm up than in winter it accounts for more gas use.
About 10k back I had Kumho t11 tires installed at Discount Tire . Very good tire and you save a good deal of money over some others. They are well liked in "Consumer Reports".
You know if I could get a suv that gets the same gas mileage as my Corolla at the same price as a Corolla and great reliabilty I would consider one. These are the main reasons I bought my Corolla.
I change mine myself. I have no set minimum mile change. I prefer to change when the weather is decent and not cold out. I`m usually at around the 5-6k mile mark when I do the change. I know that is sooner than needed but I do it anyway.
When I first saw this post listed I thought you wanted to increase your horsepower to 1.8hp . I was thinking what the heck, that`s not even 2hp, why bother. Duh, then it hit me :-)