I compared Dextron III viscosities to the synthetic's cold and hot specs and found that Mobil 1 was the closest to the properties of Dextron III. Dextron III is mineral based, while Mercon V is a synthetic blend. Some of the synthetics had much higher cold temperature viscosity which might promote some grinding in colder temperatures before things warm up. That can be hard on synchronizers. Needless to say I run Mobil 1.
