Brake Fluid Differences?

[kurokoma-kun]

Originally Posted by Loren

Look in your owners manual. It will tell you what spec you need, just like it tells you what spec of engine oil (but not what specific brand!) to use.

My owners manual says DOT 3.

I get what you're saying, that it doesn't matter under ordinary driving conditions, just for the record.

[Loren]

Originally Posted by kurokoma-kun

My owners manual says DOT 3.

I get what you're saying, that it doesn't matter under ordinary driving conditions, just for the record.

On today's market, I think you'd be hard-pressed to find a "DOT 3" product that did not also meet the "DOT 4" spec.

Here's just one example: Castrol LMA

The main difference between the two specs is temperature. DOT 3 is good to a minimum of 401 degrees, DOT 4 to 446 degrees. So, Toyota specing the system for DOT 3 means that they don't expect the fluid to exceed 400 degrees in even extreme normal use. ("extreme normal use" typically means something like one good hard full stop from a fast highway speed, btw... most normal drivers will never do that more than once in succession, and that's all the factory braking system is designed to handle)