My 2000 MB E430 makes a light whine when engine is hot after driving around 15-20 minutes or so, when the engine is cold it's very quiet. MB recommends either their Power Steering Fluid or Dexron III fluid for 2000 E430. Since M1 new Multi-Vehicle Formula ATF is compatible with Dexron III and it is synthetic fluid, I decided to use it instead of Dexron III. I tried to suck out as much old PSF in reservoir with a turkey baster, I could only suck out about 5-6 oz and replaced with M1 ATF. I'll repeat this sucking and refill until a quart of M1 ATF is in the power steering system. I'll update how the E430 steering system responds to M1 ATF.