I just checked the bottle of Febi hyd. fluid I have and there is no "Mil" spec. With regard to cost I was able to buy some for $6.82 a liter through another on-line outfit. I would rather drive it with the fluid low versus putting something foreign in it. Where did it go by the way, that it is so low?. I would stay away from using ATF. The hyd. fluid for this sys. is thinner than ATF. It is very similar in thickness and color (lack of) to brake fluid, but then again would you want to mess up an expensive sys.? How much stuff are you bringing on this trip, will it really weigh down the backend?

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member