I was looking through my wifes Mercury Sable owners manual and found a warning. The warning said that ATFs recommended for both Mercon and MerconV should not be used in transmissions for which Mercon is recommended. The odd thing is that the manual is for a 2003 vehicle that recommends the use of MerconV. The manual says that the dual fluid is fine for the Sable but then goes on to make recommendations for older vehicles. The manual even says that MerconV fluids are not "compatible" with Mercon fluids.