Changed brake fluid on my TJ yesterday. I have used Mobil DOT 4 for years (blue in colour). The stuff I got yesterday (Mobil DOT4) is a pale yellow colour. S''t why do they always feel the need to change the packaging and make other changes. Now the question is how compatible is the yellow fluid with the blue fluid? Anyone know. I have sent an email to Mobil.

Color difference assists (you) in determining when the new fluid is coming out of the bleeding tube, that's all. DOT reading is relevant but internal chemical properties are debatable - as long as you stick to good quality fluids.
Would be interesting to see if/how Mobil replies.


Changed brake fluid on my TJ yesterday. I have used Mobil DOT 4 for years (blue in colour). The stuff I got yesterday (Mobil DOT4) is a pale yellow colour. S''t why do they always feel the need to change the packaging and make other changes. Now the question is how compatible is the yellow fluid with the blue fluid? Anyone know. I have sent an email to Mobil.

If the old fluid has gone very dark just running new fluid through it might not be enough. Just replace the whole lot with the yellow stuff. If you really want to do a thorough job dismantle the calipers and clean out all the rubber grot in them. You get much more sensitive/controllable braking when its all back together, and you know all will be ok with the brakes for the next few years. Usually you don't need to replace any rubber bits unless the boots are torn.

The old sigmas were classic for blocking the pressure load valve for the front/rear brakes in the master cylinder with rubber buildup. Rear drums would stop working but in the dry you wouldn't notice.
In the wet the fronts would lock up and you would slide gracefully onwards. lol
A master cylinder dismantle/cleanout was essential for safety on these cars, donno if its needed for 4 wheel discs on the Magna though.

Uwwhhh, nasty stuff!
Yeah, it's a good idea to flush fluids at least once a year to avoid build-ups and other contaminants. I do mine twice pa generally.


If the old fluid has gone very dark just running new fluid through it might not be enough. Just replace the whole lot with the yellow stuff. If you really want to do a thorough job dismantle the calipers and clean out all the rubber grot in them. You get much more sensitive/controllable braking when its all back together, and you know all will be ok with the brakes for the next few years. Usually you don't need to replace any rubber bits unless the boots are torn.

The old sigmas were classic for blocking the pressure load valve for the front/rear brakes in the master cylinder with rubber buildup. Rear drums would stop working but in the dry you wouldn't notice.
In the wet the fronts would lock up and you would slide gracefully onwards. lol
A master cylinder dismantle/cleanout was essential for safety on these cars, donno if its needed for 4 wheel discs on the Magna though.

what if changing to synthetic fluid? read a tech article in popular mag that spoke of using synthetic fluid due to it's qualities of less moisture absorption. but to change would need to change or clean and flush properly whole brake system.

has anyone done this? did you get a better pedal feel?

i would be hisitant to mix the two fluids. in hydraulics you must use the same fluid to top up or replace as is already running in the system. if two different fluids mix they can react and coagulate so instead of having a nice thin fluid flowing through your system you have large globs of jellatinous goo clogging everything up. i'm not sure if brakes would be the same, but they are hydraulic so im assuming the same rules aply?

i would be flushing the whole system myself