Low viscosity brake fluid for self-driving car?

Jun 8, 2017
I have a Comma 3 controlling my 2018 RAV4 which basically endows it with adaptive cruise control+lane centering from 0 to 90 MPH. Basically, the RAV4 drives itself 85% of the time--highways and surface streets. Does pretty much everything except sharp turns.

The thing I've noticed is that when coming to a complete stop while self-driving, the car does so through the ABS. The car actuates the friciton brakes by controlling the ABS pump. I can hear the ABS pump working each time I approach a stopped car or a red light. It's not loud enough to be annoying, but noticeable.

I just installed some Speed Bleeders on the front calipers and bled out some of the 120k mile old brake fluid and replaced it with generic DOT 3 from AAP. I purchased some Liquimoly DOT 5.1 that I plan to fill the system later.

My question is: due to frequent use of the ABS, would there be a better brake fluid? Would a low-viscosity fluid be easier on the ABS pump? I know DOT 5.1 has to be lower in viscosity than 3 or 4, but would there be an even better fluid? Maybe a special "LV" fluid? It would also be nice if a low-viscosity fluid could quiet down the ABS pump working while coming to stops.

The car certainly wasn't designed with constant and frequent ABS use in mind, but ABS is how the car stops while in hands-free driving mode. So I'm curious about how to maximize the life of the ABS pump before I have to replace it!
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