Just wondering if there is any advantage or potential problems with mixing half and half a quart of syn. with a quart of conventional 85-140 for a rear axle oil change on a 86' Dodge W-250 with 50K miles on the odo.. I use it for snow plowing and fire wood hauling on forest trails. I almost never exceed 55mph in this vehicle but it works hard plowing and hauling, about 2k avg. miles/yr.