clutch oil/Prestone Synthetic DOT 4 does not turn "brown"

[R1150Rclean]

So when I first got my used R1150R 2003 (non-ABS) I changed the clutch oil, it was dark brown, and after ~6 months it turned dark brown again (heard that was normal on this forum). Then I replaced it with Prestone Synthetic DOT 4 oil and after 5k/1 year it looks like new. Normally when bleeding the clutch I would see a change in the oil coming out the drain line from dark brown to light tan (the new oil) did not see it this time Maybe it will keep the slave piston seal in better condition.

[bergj1986]

My understanding is that the clutch/brake fluid will turn brown because it has absorbed moisture.

Reminds me to check my clutch fluid...

[R1150Rclean]

Actually, I thought it was the heat from the transmission and Cat that made it turn brown. The syn. oil is designed to take higher temps. without breaking down (i.e., turning brown). Water usually makes oils turn white/opaque.

[Keppelj]

You may have happened across a brake fluid which doesn't absorb moisture. There are some. I've used that in a racecar though at the moment I don't remember what the brand was. Doesn't the RR owner manual spec changing brake (and clutch?) fluids annually?

[R1150Rclean]

Doesn't the RR owner manual spec changing brake (and clutch?) fluids annually?

I have been changing it every 6 months, live in a hot state, and after 6 mo. it was dark brown with the non-syn formula.

[CycleRob]

My 2.4 year old new bike has a clutch cable but I remember changing the 50R's clutch release Dot4 fluid every year. You must. Conventional brake fluid aggressively absorbs water as liquid (rain/washing) and as vapor (humidity). That water absorption makes it turn colors gradually from clear to light beer to ale to coffee to espresso. Try to change it at the "ale" stage at the latest!

It is important that you use a method that cycles clean DOT4 fluid thru the slave's full operational piston stroke many times, until the fluid runs clear. You accomplish that by pulling the lever to the bar, releasing the bleeder rapidly, closing the bleeder then releasing the lever. That cycles the slave piston so the slave's old chambered fluid is partially expelled at every opening of the bleeder. Opening the bleeder quickly more effectively mixes up the new fluid with the old stagnant fluid, increasing the amount of old fluid purged. If you open the bleeder then squeeze the lever, only the lines and the very short bleeder-hose passageway in the slave will be purged.

[R1150Rclean]

I will try that method CycleRob, and now I am wondering if the light tan color is just from the slave cylinder "old brown non-syn oil" slowly mixing with the new syn-oil. The non-syn. clutch oil turned dark brown in the reservoir too, while the syn-oil just took on a light tan color and did not get any darker. The syn-oil is designed to handle higher temps., and that is why I think it does not turn brown. I associate water and oil with a milky/opaque appearance, not a dark discoloration. Heat non-syn oil in a pan and it will turn dark brown (remember the old Mobil I commercials?), while syn-oil will not "at the same temp.".