I noticed my F6 slipped the other day going up a hill on highway in what I think was 5th and ive since been told that GW is known to effect 5th gear frictions.I got a service and trans cooler install done by CMS and was advised that the GW was the perfect option for my power output and is fully approved.Not too happy im now forking out cash to get full flush and GENUINE ZF oil put back in,Im also hoping there is no other damage to box as I don't have 6k laying around to fix a box that could well be caused by wrong oil being put in. I know there are guys on here that say GW is fine but Is it really worth saving the $250 to possibly damage the box?? What oil does Nizpro and Xtreme use in their box seen as though they seem to be builders of quickest ZF's in the country??