Since March 1996, Porshce has started using Pentosin CHF 11 S fluid instead of the automatic transmission  fluid (ATF) previously used (note: anybody with an Audi should be familiar with Pentosin).  Pentosin and ATF are miscible (can be mixed together).  Therefore, Pentosin can be used to fill or top up older model cars using ATF.  However, cars originally filled with Pentosin should use only Pentosin when power steering fluid is needed.