2011 Ford Ranger with manual transmission with 91k miles. I just did a fluid change from M1 ATF to Amsoil Manual Synchromesh Transmission Fluid 5w30. ATF is what is recommended. With only 12.5k miles on the ATF, shifting was notchy from day 1. It would resist going into gear and then suddenly engage. There was a shocking amount of iron particles on the magnetic drain plug. There was enough that the wear particles had a wave pattern on the magnet. After the change, shifting immediately felt nice and smooth. So far I am very happy with the change and even more so after seeing how quick wear was occurring with the M1 ATF.