2000 DS650. Calls for Dot 4 brake fluid. after completely flushing and bleeding both front and read brake systems (complete fluid exchange until fluid ran clear) I was putting the bottle away and noticed it was Dot 3 synthetic.

Here is what I know. Dot 3 has a boiling point of around 400F. Dot 4 BP around 440F. Dot 3 synthetic is around 470 BP, so I came out good in that respect.

Since I did not mix old and new fluids, is there any concern that it's synthetic, or is it just that BRP screams "NO SYNTHETIC" for warranty reasons?

Thanks

 

OK. This is what I believe so far...

DOT 3 dry BP is ~400F, DOT 4 dry BP is ~440F, DOT 3 synthetic dry BP is ~470, and DOT 4 synthetic dry BP is ~500F. These are all glycol based fluids, and the difference (just like motor oil) is the additive packages. I believe the reason that once synthetics came around (after DOT 4 came out. I'm not going to talk about DOT 5 at all here) the manufactures made DOT 3 synthetic is for people that feel the need to keep a DOT 3 product when the brake fluid reservoir cover says "USE DOT 3". Same idea applies for DOT 4. The difference in BP for DOT 3 syn and DOT 4 syn falls along the same lines.

I think I am fine. It would be nice if an expert chimed in though.

 

I can't get a good consensus anywhere. More digging about DOT 4 shows it contains boric acid (DOT 3 does not). Under pressure, boric acid decreases friction in sliding components, so that is my best guess why I should stick with DOT 4 if Nissian is counting on the added lubrication to keep the calipers working well.

Luckly, it's pretty easy to flush and bleed the brake system on the DS650, and a small bottle of brake fluid cost less than $3. Ill be flushing the DOT3 before I go ride this weekend.

Hope this helps someone else down the road.