Jason, I have changed my fluid at 35K and at 50K (w/filter). I used Redline D4 ATF w/no problems. The car actually seems to shift better, especially when cold. ZF recommends Esso LT 71141 which is suppose to be a semi-synthetic. It is probably what Audi/VW, BMW, Jaguar, and others that use a version of the 5HP24 transmission use re-bottled with their label.