If you're overseeding your lawn this year, we highly recommend using only Fescue seed.  Turf type Tall Fescue is the most disease and drought resistant type of grass for the midwest.  With extreme heat the last two summers, we have seen superior drought resistance with fescue as opposed to Bluegrass.  Most of the brown spots in your lawn this summer are most likely the bluegrass plants, not fescue.  There are many awesome varieties of fescue available.  Please call us if you want recommendations on what type of seed to use.