6bangr

I am about to start my new clutch install including the flywheel, slave cylinder & clutch hydraulic line. I’m probably going to be upgrading the brakes next year and plan to switch to dot 4 brake fluid.
If I flush the brake fluid in the future I imagine there will be some residual dot3 fluid in the clutch slave cylinder. Would that residual dot3 fluid cause any issues if I switched to dot4 when doing the brakes?
basically is it a bad idea to mix dot3 and dot4?

algregory

I'm an Amsoil fan. Just for drill I wondered if they had brake fluids. They have "3" and "4" and call "4" "Racing". Yet, far as my quick look can tell, they describe the two exactly the same, except for "3" and "4" where "3" is High Performance and "4" is Racing.

I used to change the brake fluid in my last car every year of so, yet have not done my '05 GT at all. I've been a motorcycle rider for years, used to change that fluid yearly also, but, getting older (67) and have not done my '04 Yamaha FJR1300ABS at all. On cycles I recall that fellows would switch to Silicone Brake Fluid so it would "be better" and not hurt their paint either. But, I seem to vaguely recall that the change over had to get the "DOT" fluid out of there big time before installing the Silicone fluid. FWIW

Derf00

Dot 3 and Dot 4 are compatible with each other. The difference is the boiling Temp (DOT 4 is higher).

DOT 5 is silicone based and is NOT compatible with 3 or 4.

gmoran1469

And for those who don't know... DO NOT USE DOT 5 SILICONE BASED IN A CAR WITH ABS.

Go get a can of Motul ATE Super Blue or if you prefer, get the non-dyed clear version (some claim it dyes the plastic permanently). Either drain the system and flush for peace of mind or do like most others, drain it as much as you can, fill it fresh, drain it, fill it, bleed it.

6bangr

Thanks for the info. I'll suction out the reservoir and bench bleed the new slave cylinder with dot 4 then flush out the rest of dot3 when doing the brakes. I think I'll avoid the blue stuff just in case it does actually stain. My coolant reservoir is stained which makes it difficult to eyeball the level without actually having to take the cap off.