All things being equal - which they aren’t - other than dot 5.1 brake fluid having a higher boiling point , would there be any real problem doing the brake fluid flush with Dot 5.1 fluid vs. Dot 4 listed on the cap ... isn’t the Fancy new Formula better ?
In the past I thought nothing of changing to Dot 5.1 in a New MINI or 1990 Miata used for track day outings ?
But what does the chemistry say ?
Thanks,
Don
DOT5.1 and DOT4 are overlapping specifications for interchangeable fluids - think of DOT5.1 as being an optional spec for the highest boiling point DOT4 fluids. But because it's optional, there are fluids with a DOT4 spec with higher boiling points than some DOT5.1 fluids, so you need to check the temperatures to be sure.
Just don't use DOT5 in a DOT4/5.1 system, it's a completely different and incompatible fluid. Also you may want to go with a low-viscosity fluid (labelled DOT4LV or DOT5.1LV) for cars with ABS, some high-temp fluids have a higher viscosity that ABS systems don't like, so some fluids have the LV spec so that you know ABS will work well on them.
Systems that require LV say LV.
I have heard that even though DOT 5 is technically not miscible with DOT 3/4, you can use it mixed in a system, you just don't get the benefits of either. Meaning, DOT 5 doesn't absorb moisture, so any water that collects in the system can boil or freeze. I forget if 5 is denser or less dense than 3/4. Freezing in the reservoir, okay. Freezing in the caliper, not so okay.
Thanks for the reply Pete,
A similar post on a motorcycle forum set off a Firestorm of biblical proportions, without any real facts backing up the opposition other than "That's what the cap said" and so it was written.
Don
Bosch 5.1 is cheap and good enough for the TNIA I did (haven't changed it since, reminds me I should). It's the only bottle I keep on the shelf now.
Honestly if you flush the fluid regularly you can ignore the wet boiling point.
If you are using streetable pads, you'll probably find their thermal limit of uselessness before the fluid's. Again, IMO.
Use what makes ya happy, it's not a religion.
Now let's talk about the weirdos who see that you can buy brake fluid in gallon jugs and want to use it in the cooling system... Man that would smell bad!!
PPS: Yes , I keep asking the question until I get the answer I want to hear ! :)
In reply to Pete. (l33t FS) :
Now let's talk about the weirdos who see that you can buy brake fluid in gallon jugs and want to use it in the cooling system... Man that would smell bad!!
well it would never boil over :) even after the engine was seized ;(
You'll need to log in to post.
