Mixing Different Dot Fluids

Drain the fluid and refill with new after using the new fluid to flush the system, very straighforward if you are just doing the clutch.

 

just dont mix with synthetic other than that wont be a prob, but flush it anyhoo.

 

I agree with @finm. I don't see it as a problem unless you mix synthetic with mineral.

That said if I was installing a new slave I'd do exactly what @Red998 suggests and flush out all the old stuff and put in new. Any of the DOTs should be fine except 5.0 which is to be avoided at all costs as its not compatible with any of the others and (from what I've been told) it's incompatible with the seals too.

Depending on the specs some DOT 4's actually have a better spec than some of the DOT 5.1. But for clutch use it really shouldn't be an issue.

 

Replace with new fluid. Takes 5-10mins on clutch. Very simple job. In fact it takes about 30mins to do all the brakes too. I got some of that Motul 600 and did the lot when I was fitting the oberon.

Still cant get rear brake to work though. But as I never use it....guess i will have to get a new m/c for it though. I swear the lever pin is too short.

 

There will be no problem as long as you use either DOT 4 or DOT 5.1 fluid, both of which are glycol based. It makes sense to flush plenty through, but there's no reason to have any worry about a degree of intermixing. My clutch cylinder has been just fine ever since I stripped it to replace the seal, and replaced the original fluid, whatever it was, with DOT 5.1 (which was simply what I happened to have).

That said, we need to be careful about terminology, and my understanding is that the only "mineral" fluids (which are petroleum oil based) are those used in unusual cases like some Citroen braking systems. You should never, ever, use "mineral" based brake fluid in any system not designed for it, and that means it should never be used in a motorcycle system (unless Citroen once made bikes?).

DOT 5, as previously mentioned, is silicone based, and incompatible with DOT 4/5.1 - I get the impression it is going out of fashion, and I've never had a vehicle which needed it - I think the US Dept of Transport made a mistake by creating the risk of confusion between 5 and 5.1 - I wonder why they did not use 4.1? It would probably be correct, but confusing, to describe either glycol or silicone types of fluid as "synthetic" because they are manufactured chemicals, rather than something distilled from crude oil.

 

Ok...whats the best way to flush it out (twin brakes) Simply keep pumping new thru until you have emptied the resevior about 5 times?

 

Mix Dot 4 with Dot 5.1 @ 50:50 and you end up with Dot 4.55 :Happy:

 

My mistake @Recidivist I was trying to differentiate between DOT 5.0 and the others and was too dammed lazy to look up the terminology.

Many Thanks for clarifying