Quote:
Originally Posted by Maynard
More specific to this issue is that the track brake fluid (Motul etc) is not low-viscosity, so if you get winter temps down near freezing you will want to swap for factory fluid each winter - the track fluid won't work right in the ABS when real cold, and the low vis isn't real good at track temps (apparently tolerates them, as per the boilpoint specs, but not .
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Winter viscosity is something I'm concerned with as well. It obviously gets really cold here in Minnesota, and I REALLY want my ABS and all the related stability control to work well in icy, sub-zero conditions.
None of the high-temp/track fluids are remotely low-viscosity at the standard test -40C temp. Castrol SRF is listed at 1300-1500 mm2/sec. (Compared to 2.5-3.5 at 100C.) Motul RBF600 is 1750 at -40C. Plain DOT 4 fluids, like ATE SL are also around 1400. So, the Castrol SRF isn't any worse than a standard fluid.
I can't find a reference for the BMW brake fluid, but the Pentosin LV I use in the winter is listed at <700. ATE SL.6 low-vis is also a max of 700. Less than half of any of the standard or track fluids. If fluid that is half as thick will cycle my ABS faster and more precisely, that's what I want in the winter.
I swap my summer track fluid for low-viscosity in the fall. And back to track fluid in the spring. Usually when I swap the winter tires on/off. Kind of a pain, but worth my peace of mind. And I'm definitely sure I don't have old water-saturated track fluid that way also. And I'm getting really good with my pressure-bleeder and the ABS cycling process.
