Another thing to think about Pretty much every Automatic car ever made has had water to oil cooling, that's almost every manufacturer, every model, millions and millions of cars, how many have issues? I personally have seen 2 ZF heat exchangers fail and a similar one on a Golf about 8 years ago. And have also seen 2 cars that owners have fitted air to oil coolers on stock FG's and now do not like their shifting and yes the oil level was corrected, one of them was around 60k klms can't remember the other one though