Yes but no.

I used to use baby oil in my old Hydro Magura calipers. (actually, dad and I both did)

I remember having to re-bleed a LOT. It never felt very good through the levers either. Overall it "works", but I would only say "Emergency use only"

 

Don't do it or, then again... maybe your purpose is to be an example to others of what not to do?

As a father and former master diaper changer - seriously, pure mineral oil has no scent - the johnson stuff at least has something to make it smell nice. You don't want anything else in your brake system.

Back in the old days before shimano sold big bottles of their oil I bought a bottle of Febi Bilstein 6162. 1L was $9.99 at local auto parts store. Have been using that bottle for 5 years now, many bleeds, many bikes, no issues and I still have 850 ml left. The 1L shimano bottle is now $26 on amazon, I'd still get the 6162 for $12.

https://www.amazon.com/Febi-6162-Power-Steering-Fluid/dp/B007XB4QPY

 

You can get unscented mineral oil from the pharmacy pretty cheaply. IDK anything about it's hydraulic properties. There are specific physical properties appropriate for brake fluid that may not be exhibited to the same degree by suggested alternatives. Proper viscosity over temperature, lubrication properties, low volatility, high boiling point, compatibility with seals, hoses, etc.. If you use anything other that what's approved, you're conducting an experiment.

 

You're not the first to ask and won't be the last. Just don't do it. There are better ways to save money on maintenance than this.

LOL @ too many bottles comment - it's too true.

 

Mineral oil intended for machinery or brake systems is more commonly referred to as 'Hydraulic Mineral Oil' has a multitude of additives. Most commonly, they contain anti-foaming agents to reduce foaming under high heat applications, corrosion inhibitors, and anti-wear agents. This mineral oil is has a lower viscosity than drug store mineral oil.

'Drug Store' Mineral Oil, is somewhat thicker and heavier than hydraulic mineral oil. And, the stuff we use as humans is used as a laxative, usually contains perfume and consumable additives along with shelf life stabilizers.

http://forums.mtbr.com/beginners-corner/shimano-mineral-oil-alternatives-740756.html

 

'Drug Store' Mineral Oil, is somewhat thicker and heavier than hydraulic mineral oil. And, the stuff we use as humans is used as a laxative, usually contains perfume and consumable additives along with shelf life stabilizers.

i'll give this a try next time things get "backed up"..

 

Mineral oil just means it is a petroleum derived product and is really a catch-all phrase for almost all non synthetic oils. If you look at the labels, even generic motor oils will say mineral oil as the main ingredient.

You can use any lower weight fork oil, with matched viscosity, as these are not complex oils. If the viscosity is higher, the calipers wont retract correctly and you will have more brake rub. I bet Shimano's oil might even be the same exact stuff as say Rockshocks 5w fork oil. To test, you could use any small funnel with a small enough exit hole to be able to time 30cc or so of oil to drain out in like 60 secs. Lower viscosity wont hurt performance.



What ever you do, dont use auto transmission fluid. This stuff is intended to have high static friction so your trans doesnt slip when in gear. It is less of a big deal in brakes but amazes me why people put this stuff in shocks or forks.

 

What ever you do, dont use auto transmission fluid. This stuff is intended to have high static friction so your trans doesnt slip when in gear. It is less of a big deal in brakes but amazes me why people put this stuff in shocks or forks.

There are many areas around the globe where getting quality components or fluids is difficult or cost prohibitive and ATF is readily available and regularly used in Shimano brakes. There have been several threads where some have used ATF for years with no issues or problems.

Shimano fluids are easy to get here, so I'll just stick with that.

 

If you ask Shimano, they'll tell you the "mineral oil" part is misleading. It's their special Shimano brake fluid, formulated with very specific properties, and not interchangeable with any other fluids. They claim even other bike mineral oil fluids are incompatible. I've read somewhere (can't find the source atm) a Shimano tech rep explaining that using Finish Line mineral oil will cause the shape of the square-edge piston seal to permanently change. Same with Magura fluid. That supposedly decreases pad retraction and would lead to more rub. If you ask Shimano, they probably wish they had never called it "mineral oil" and instead just called it "Shimano Brake Fluid" (or come up with a catchier name like Magura's Royal Blood).

But that's the kind of thing you'd expect Shimano to say. I think there's reason to be skeptical about how absolute Shimano's position is. I'm sure we all can find people who have run other hydraulic mineral oils in Shimano brakes and claim it all works fine.

Tektro/TRP also says to use their own oil and no other mineral oils. The stuff they sell looks identical to Shimano oil. I've heard that if you call them and ask, they'll confirm it's perfectly OK to bleed your TRP brakes with Shimano fluid. It's possibly the same exact stuff.

What I think most likely is that Shimano (and likely others) did screening tests on a variety of already-available fluids from the automotive/motorsport/aviation/military worlds and selected one that worked for their application. All their subsequent product development and qualification testing would have been done using that oil, and they can't necessarily predict what another formulation might do.

If you knew the exact correct formulation, you might be able to buy it in bulk for cheaper. If it's a MIL-spec hydraulic fluid like AeroShell 41 you might get it for $10/L. If it's a specialty automotive like Pentosin 7.1 it'll probably work out to the same $20-$30/L most brake companies try to charge.

Frankly, for my peace of mind, the 1L Shimano bottle is the way to go. It's your mountain bike brakes after all. But it's a fun topic of conjecture.

 

You aviation guys might agree with this...

I have often thought that Shimano Brake Fluid is possibly a MIL-H-5606 hydraulic fluid derivative, an aviation mineral oil-based fluid. Perhaps not even a derivative, but straight unadulterated 5606.

 

I have often thought that Shimano Brake Fluid is possibly a MIL-H-5606 hydraulic fluid derivative, an aviation mineral oil-based fluid. Perhaps not even a derivative, but straight unadulterated 5606.

I looked into this a while back and concluded that it was likely a 83282 or 87257 type fluid based on the boiling point and viscosity. The boiling point for Shimano brake fluid is 280°C which is pretty close to either of the aforementioned fluids and much higher than 5606 based on some MSDS and spec sheets that I found.

 

Its mineral oil as in petroleum oil, not as in baby oil. You might as well pour cooking oil in your brakes if you're going to be using baby oil. The fork oil would probably be a better choice.

Im using pentosin 11s. I let it mix with shimano fluid. I don't anticipate any issues with this but its not advised by pentosin or shimano.

 

Baby oil = mineral oil + additives to make it smell nice

https://en.wikipedia.org/wiki/Mineral_oil

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How can you be sure you got all the baby oil out of the system? Surely tiny quantities remain to affect the performance, in the same way a full fill does, by a little bit.

 

Misplaced enthusiasm to worry about tiny quantities remaining. Do a full flush and go ride.

 

Of course Seth's done this..... his review of one year on baby oil.

 

Just burped an old tektro Auriga front hydraulic brake I got on an old set of toras. Topped it off with johnsons baby oil from the bathroom to see what happens. Works alright thus far, Will keep you posted.

 

It will work fine, but would likely be problematic in a cold environment