View Full Version : Brakes: Dot 3 or Dot 3 Synthetic ?

07-22-2012, 07:56 PM
I run Dot 5 Silicone Brake Fluid in both of my cars so I couldn't answer this question from a car buddy of mine. He inadvertantly purchased Dot 3 Synthetic Fluid and was wondering if it is compatible with standard Dot 3 fluid. I believe that they are nearly the same and are compatible but wanted to hear back from you gents just to be sure.

Thanks for the help, Harv :confused:

52 Ragtop
07-22-2012, 08:29 PM
I'm pretty sure they are compatible, I'll double check tomorrow! I sure hope they are! as that's what I used in my Avanti last year!


07-23-2012, 09:43 AM
Good morning Harv. Dot.3-4 and 5.1 Are not compatible with synthetic brake fluid.
Do not mix them.

nibbs53 Patrick.

07-23-2012, 12:49 PM
Jim / Patrick .... thanks for the followup. I did just read a bit more about DOT Brake Fluids and they did agree that mineral based fluids are not compatible with synthetic types. Thanks again for your help on this. ..... Harv

07-23-2012, 12:54 PM
It would appear that there is some confusion about the classifications versus the definition of synthetic.

A Google search will quickly show that All Dot 3/4 classifications whatever the other definitions included are, By definition, compatible. As are the Dot 5.1 fluids. They are all manufactured and formulated for compatibility.

Dot 5 is the lone out-liar due to it's silicone base. If you really look at the definition of synthetic, All brake fluids are because they all require modification of a base structure. Why the industry has allowed this to happen is beyond me. Probably more marketing hype than fact.

Ref: Bob the oil guy and a plethora of other posts. http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2332203

JMO, Bob