Hello, I owned a 1999 V70 base for 49 months during which time I added ~66,000 miles to the original owner's 49,000. He and his Volvo dealer thought that someone had followed the incorrect instruction in the owner's manual stating that ATF be used in the power steering system. I was told by that dealer and others that synthetic fluid was called for. The apparent mistake in the owner's manual was "due" to the mid-cycle enhancements made to that car. The seperate P/S reservoir (off the pump and moved to the right fender adjacent to the coolant overflow bottle) was said to be a tip-off. My growly, pulsed steering function was cured by a flush with Volvo synthetic fluid. That fix lasted for 36 months. The buzzing returned. It grew to a constant noise over a 2 month period. I replaced the pump with a salvaged unit said to have been taken from a 2000 or 2001. I reflushed with synthetic. Now I drive a beautiful 2002 V70 base and the manual says to use ATF in the P/S pump as top off and that fluid changes aren't necessary. What input does anyone out there have? I'm considering a complete flush with synthetic. Comment: The owner's manual seems soft in spots. Thank You, George and Kira