Can't use dot 5.1 in a 1st gen?
 

Some mechanic told me today that I had to stick with dot 3 brake fluid. And that I may get no stopping power at some point if I use dot 5.1. Does anyone else in a 1st gen use anything but dot 3? I can't see why it would make a difference, it just has a higher boiling point.

Something in the fluid will eat the seals of a system not designed for DOT 5, if I remember right.

DOT 5 is worthless, IMO. Use some high quality DOT 4 stuff.

DOT 3 and DOT 4 are basically the same thing just DOT 4 has higher standards, correct??

I would suggest you read the labels very carefully. There is a difference between DOT 5 and DOT 5.1. The DOT 5 is Silicone that has been produced for some time now, and has specific advantages over DOT 3. I have the DOT 5 in my Austin Healey 3000 because it will not absorb moisture, and I wish to retain the origional brake components.

I use Castrol LMA DOT 4 in all the race cars. The major difference between DOT 3 and DOT 4 is compatability with natural rubber components in some brake systems. The older British cars like, and some even specify DOT 4. In the case of the Castrol, LMA stands for Low Moisture Absorption.

I have used all different kinds of brake fluid in the race cars, and have found the Castrol to be just as good as the others.

Hope this helps in some way. Understand, this is not the difinitive essay on brake fluids. It is only my experience based on the last 25 years of building and driving sports cars of many different marques.

db