The Michelin Ice X tires on my wifes 93 Topaz have a max rating of 51 PSI. So when the weather was good all summer I ran them at fifty (from the previous 32). It made almost 2 mpg without any appreciable wear abnormalities. The ride is harsher but the wear and mileage are great.
Note, I have experimented in snow, ice and rainy weather and from experience hard tires make great sled runners in the white stuff. So whenever the weather is bad a lower softer more compliant tire makes a world of difference. By the way I drive about ten K miles per year in the snow alone in my work. About thirty K total on my work car so mileage is important.
