So I was flushing my sons brakes on his mtn bike and I ran out or shimano brake fluid. Long story short, I used johnsons baby oil instead. Been working fine for months. Anyone else try this? Any reason(s) not to?

Seems a great idea. I love experimenting with the brakes of a vehicle capable of 40 mph in traffic, which offers no physical protection for the rider.

Just curious: how volatile are the perfumes and other additives in Johnson's baby oil? Is it compatible with the seals, lines and other polymer parts in the brakes?

since you can write about it , now you can use the same internet to get the right fluid..

Shimano & Magura, does use a Mineral oil , many other brakes use DOT stuff like cars .

hope your child survives your experiment.






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Baby oil is primarily White oil/Paraffin oil. A very harmless substance.
Anything OK to smear on baby skin, and is given by the pint to constipated horses is hugely unlikely to upset polymers and plastics.
I’d be wary about performance variation over temperature though.

To continue your digression, I've never seen a vet administer Johnson's Baby Oil and I probably never will as the perfume in it has only been tested topically, according to the FDA. See "For external use only" on the label.

Not sure how the safety of a baby's bottom will translate to a hydraulic brake, but maybe it will give the OP some comfort. Guessing about it's effects on a bike brake system could be exciting. How hygroscopic is the perfume? What is its vapor pressure and viscosity versus temperature? Does Johnson's Baby Oil's viscosity index match that Shimano's specification?

That is a hack in the same way wrapping a leaking radiator hose in duct tape is a fix...that is, fixed until it can be replaced ASAP.

Bad idea. Mineral oil is a generic, nonstandardized term as far as brake fluids go. Mineral oil for various bike brakes have additives for any number of reasons. In particular, I know that interchanging Magura fluid and Shimano for one another can cause brake failure.