Mountain Biking - Mineral OIL -DOT fluid question

Hi guys

I need some help here. I am sorry that i have troubled you all with my disc brake questions so far. I had my brakes bled 2 weeks ago by my LBS , Team-Skene at Cardiff,UK. The brakes work however they dont have full power....the front cant lock yet...wereas the rear can lock if dirty and not cold. Anyway.
Yesterday i opened the reservoir cap to add some oil and i noticed that the color of the oil inside the reservoir is different than the shimano oil that i have in bottle. Shimano OIL is kind of red color while the oil inside my brakes is like a natural oil-color. I have noticed that at the LBS as well when they bled them. I am mostly concerned with the possibility that the bike shop bled my brakes with DOT rather than mineral oil... they said they used the shimano bleeding kit however...Anyway i added some red oil in the reservoir and it mixed with the existing oil...Can i tell if i have DOT or mineral on my system? Its Deore XT so its supposed to have only mineral in it. The oil smells a bit like baby oil...and i need some help here ...thanks guys ....i ll appreciate quick responces because they got me very nervous and its sunday and everything is closed here.

First of all; never mix any brake fluids until the manual or brake fluid code tells you so!!!

From the shimano website; "The use on systems with DOT fluid may damage the rubber plate.

Note: Never mix different brake fluids. Use only genuine Shimano mineral oil. If other types of oil are used, it may cause problems with brake operation and cause the system to be unusable"


DOT based oils are mixable IF they are FULL synthetic, with modern oils you can mix DOT 4 with Dot 5.1

You can recognize DOT fluid because its aggressive to paint and it bites on your skin.

Most mineral oils are not mixable; since you mixed two kinds, you probably need to bleed again.
Contact your LBS and explain the situation

Dude, about the braking power as we have told you before and will tell you again that is gonna come with some time. Disc breaks dont up and stop you on a dime, it usually takes a couple of rides to do, and XT's at the lever generally do feel squishier. My hopes feel more solid than my Bro, but the XT's have a little more power.

Ok i got some of this fluid on my second bike with a paintbrush and nothing happened!!!!! It didnt come off or anything...paint is ok. Also my fingers are ok no irritation or anytheir either so i guess its mineral right?
Thank you all for the replies...i owe you.

Originally posted by math2p14
Ok i got some of this fluid on my second bike with a paintbrush and nothing happened!!!!! It didnt come off or anything...paint is ok. Also my fingers are ok no irritation or anytheir either so i guess its mineral right?
Thank you all for the replies...i owe you.


Um hi.....why in gods name did you post the same thing 2 times again? Dont you get it?

I opened my internet explorer twice and i posted on both windows ....when you are a bit anxious you do make mistakes...

:beer: dont be hard on me for an accidental posting

The Shimano systems are designed to be used with mineral oil. If you are questioning which one was put in you system and now you have mixed them i would suggest draining the system and putting the mineral oil in.

"After you fix or replace the damaged line, you'll need to bleed your brakes, which brings up the subject of hydraulic fluid. In general, disc brakes use one of two varieties of hydraulic fluid: mineral oil or DOT fluid. Unfortunately, there are different concoctions of each, and you shouldn't mix the different kinds-ever. Don't mix Shimano's mineral oil and Magura's mineral oil. Even more disastrous is mixing or replacing DOT fluid with mineral oil, or vice versa. Doing so will probably eat all the rubber seals in your brakes and cause costly damage and a severe case of no brakes. The only quasi-exception is that you can replace one DOT variety with another-for instance, you might be able to replace DOT 4 with DOT 3 (the larger the number, the higher the boiling point of the fluid). However, you must flush out all the fluid you're replacing, which is time-consuming. In the end, you're simply better off just sticking with the fluid that comes with your brakes. "

Here is the link to the info I posted for you.

Mixin' fluids (http://205.147.231.78/mbhelp/maintenance/brakes/)

Well i didnt mix them exactly...they seem to be both minerals since they dont affect paint or skin. I just added a tiny drop in the reservoir in order to close the cap again. Do i need to rebleed just for a drop?

I have never mixed them but look at it like this, you are flying down a hill and low and behold, your seals give way and you can not stop. When it comes to such things as brakes I want to be compleatly sure they will not fail when I need them most.
Personaly I would drain the system and refill it. Aslo, if it does destry your seals you will not only have to replace the fluid but also the seals. Not worth the expense in my opinion.

The bike shop used another mineral oil. If they had some older magura mineral oil sitting around it would wont be red...more green, or natural color! You said it smelled like baby oil...so it IS mineral oil! If you mixed them it's nota huge issue...the only difference would be in the weight....i.e. just like fork oil(which alot of it is also mineral oil).

Here's an idea...since you have brought the thing to you LBS a ton of times..instead of bring it back again...try and bleed em yourself and see what happens, if you screw it up oh well you were gonna bring it back to them anyways!

Don't worry about the oils...the stuff in there is mineral oil. If you smelled brake fluid it'd be pretty harsh..nothing even close to baby oil. :beer:

Thanks guys. Just talked to them on the phone. They said its mineral 100% and they use it on all shimano brakes. They also said that its compatible with shimano oil for mixture as long as both are new. anyway they look like pro guys so i ll trust them for the time being. If they screw up they will probably have to buy me new brakes ....

Yannis.