DOT 5.1 is just fine--actually it's your best bet. DOT 3, DOT 4 and DOT 5.1 are all compatible. They are all hydroscopic (sp?) so they absorb water and protect your calipers from corrosion as long as the fluid is changed every 2 years. It gets darker as it absorbs moisture. Silicone-based fluid is labeled DOT 5 (as opposed to DOT 5.1) and should not be used in systems calling for DOT 3, 4 or 5.1. Note that the 3, 4 and 5.1 fluids will attack paint quickly if spilled so keep water around to use on any spills. DOT 5 is used by some manufacturers because it won't eat expensive paint (Harley uses it) and racers use it because it does not absorb moisture which can boil at racing temps. Hope this helps.

Jeff

Dot 5 costs a bit more but I find that as long as you flush out the old fluid well you will have less problems replacing seals in vintage parts. Plus it does not eat paint! I have used dot 5 in my Datsun for 20 years as it has natural rubber seals, (dont know what the duc has) and I dont care to change parts or fluid if it does not leak. When I do a change the old dot 5 it makes a great tire shine, now thats recycling.

I replaced the fluid and flushed it completely with 5:1
and it has performed perfecly with a solid feel in the
brake and clutch hanles. By the way on the top of the
brake and clutch oil (containers??) it is written Dot. 3-5!!
Ithought Dot 5 was a no no?? O well all is fine now.
Krakan :thumbup: