After noticing a considerable improvement in engine noise after changing to GC from M1, I went back on the search. First store I went to in downtown Grand Rapids had 17 M04's still on the shelf. For those still in search of GC, here's a pattern I have found. The closer you get to the more urban, older parts of town, the higher your GC scores. On my trip to Chicago, it was apparant that the more upscale, nicer locations had been picked clean of GC long ago.(as verified by the employees) My score yesterday was in a rougher part of town. Have seen no change in mileage from M1 in either of our daily drivers. Thank You Elves.