I did over 600 miles yesterday from the northern NY 'burbs to within 75 miles of the Canuckistanian border in northern NH and back, interstates and back roads in all sorts of weather at all sorts of speeds and not a problem with stock tires that have ~40,000 miles on them. There is something not right with your car.
ps: ooh I had my best mpg tank ever at 34 with an avg speed a little over 70mph
