Motul RBF 660 - 135i safe?

[OLEK135i]

So a box fell off a truck and I now have some Motul RBF 600 and Motul RBF 660. I have seen plenty of posts recommending Motul RBF 600, but none for Motul RBF 660. I have stock 135i calipers and am running Hawk DTC-70 front DTC-60 in the back for track days. I am also running stoptech SS brake lines. I have 2 track days coming up at Road America and plan to flush the fluid after the event. Can I run Motul RBF 660 for the event and replace with Motul RBF 600 over the winter (till next track day)? Or is 660 harmful and better off sticking with 600?

[jordantii]

Yes it's fine DOT 4, higher dry boiling point.

https://www.motul.com/us/en-US/produ...%5Brange%5D=25

[jordantii]

You're welcome.

[dcaron9999]

I replaced my oem fluid with rbf-600 a couple of weeks ago, and bled my brakes thoroughly, including lightly hitting calipers with a rubber mallet to get all bubbles out. Brake pedal feal was amazing afterwards.

Been to maybe 10 lapping events since, and no brake fade or very tiny amount on stock fads.

In the back of my mind, wondering how long the fluid is supposed to last under these conditions. My pedal is not as firm, but still quite amazing, like any properly maintained BMW vehicle.

[pj.rodriguez]

Can anyone enlighten me on the harms/benefits of using DOT 5.1 vs. DOT 4 brake fluid?

[jordantii]

This is from a guy I know and trust.

http://www.stoptech.com/technical-su...rs/brake-fluid

[Sauce]

The only downside is you really should change it sooner than 600, but it has a higher boiling point. If you don't track a ton 600 is great, big track junkies go for the 660.

[OLEK135i]

Awesome. Thank you guys for all your help. Had a death in the family, so it took a while for me to look at the forums.

[PrematureApex]

Originally Posted by dcaron9999

I replaced my oem fluid with rbf-600 a couple of weeks ago, and bled my brakes thoroughly, including lightly hitting calipers with a rubber mallet to get all bubbles out. Brake pedal feal was amazing afterwards.

Been to maybe 10 lapping events since, and no brake fade or very tiny amount on stock fads.

In the back of my mind, wondering how long the fluid is supposed to last under these conditions. My pedal is not as firm, but still quite mazing, like any properly maintained BMW vehicle.

Brake fluid doesn't "wear out" per say. It begins to retain water. The reason you pay so much for fluid is not only the high "dry" (i.e. fresh) boiling point, but also generally a pretty damn high "wet" (i.e. old) boiling point.

In fact, if you were going to put fresh fluid in for each track weekend, you can get MUCH cheaper fluid with a sufficiently high dry point to the extent that it doesn't make sense to put in some of the top of the line fuild if you're going to bleed it out after a few weeks anyway.

With any of the top-shelf fluids, even the wet point is high enough to make boiling fluid not a real concern, at least at somewhat sane power levels/tire compounds/downforce/weight. That's the benefit. You don't have to change it out very ofen at all.