I want to change my front master on my 79, I found some on the Bay but they say use Dot 4 now on my wing they say Dot 3 my question is, can I use Dot 3 oil in a Dot 4 master? this is a new master.
Front Master
- Thread starter flash2002
- Start date
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hmmmm not sure ...someone will know this...
I have always heard, and read, that the only difference is that DOT 4 has a higher boiling point which means your DOT 3 might get hotter quicker in higher breaking situations.
Dot3 is glycol and glycol ester based fluid and has a lower dry and wet boiling point then Dot4 which is glycol and borate based. The two can be mixed in emergency if caught where the recommended fluid for your system is not available. The main difference is the boiling point, Dot3 has a lower boiling point than Dot4 and will overheat quicker and cause mushy pedal or no brakes at all. There is a Dot5 which is a silicone base fluid with even higher boil point. The higher the rating, the higher the boil point, the higher the cost but the better the fluid. Brake fluid absorbs water thru the atmosphere, that's why they recommend it be flushed regularly and replaced. The water it absorbs causes the internal pitting and rusting of the master cylinders and calipers. I personaly use Dot4.
OP
OP
So in other words, I could put Dot3 oil in a Dot4 master with no problems to rubber in the master.backlander":e00wy62q said:
I would use whatever the manufacturer of the master cylinder recommended.
carl62cycles
Well-known member
Great info......right on the Dot :mrgreen:
