On a hybrid I had read once that you need to be concerned about rolling resistance if you're trying to maximize mpg. There was a report a while back on what tires were best and I think they were the Original Equipment tires every time. ;)
From CR: "A tire's rolling resistance does affect fuel economy. For that matter, CAFE is so important to most vehicle manufacturers that they demand their suppliers develop low rolling resistance tires to be used as Original Equipment on their new vehicles. In order to meet these demands, these tires are often designed with a priority on reducing weight and rolling resistance and are molded with slightly thinner sidewalls, shallower tread depths and use low rolling resistance constructions and tread compounds."
