I use valvoline conventional in my diffs, truetracs don't work right with synthetic oils. In my research valvoline was rated highly and Surprisingly is one of the only conventional diff oils my local auto parts store sells. Almost everything they carry for diff oil is synthetic. I also change my diff oil more often than recommended because when I go wheeling I usually have my axles in water quite a bit. So the conventional saves me money too.

 

Same here!