At my exact location in ZipCode 92586, FM Signal Analysis shows four stations co-channel at frequency 88.1. KRTM (Rx -66.6) and K201CD (Rx -81.3) show up in the table, while KKJZ and what looks like K201?? (both around Rx -98-99) only make the chart below. If Fm Signal Analysis is done using just the ZipCode (no elevation), KRTM and KKJZ disappear entirely. Yet both at home and in my car many miles away, KKJZ is the only station received at that frequency. From RadioLocator's station coverage maps, I am just at the outside edge of KKJZ's fringe reception area and well outside of the fringe reception areas of the other stations.
So, fine for me, as KKJZ is the station I want and I will put a yagi on the roof for better reception. But, what happened with your signal analysis?