I've got a 2000 VW 1.9 TDI with the OM1 trans. It's been slipping a bit lately, and won't go into gear cold without a little rev. Planning to change the ATF & filter. 220K miles, never been changed. I have a gallon of Dexron III sitting on the bench. Will that do, or should I be buying the $25/qt VW stuff? Thanks for any advice!