The Stovebolt Site Forums The Shop Area Driveline What brand/type brake fluid for 1955.2?

Working on the brakes and need to top of the master cylinder. The manual says to use "SAE 70R1 such as Delco Super 11" and I found some on ebay; but I didn't know if there was something more modern I could use.

This is my master cylinder type: http://chevy.oldcarmanualproject.com/gmc/5559mm/5559mm173.html

Thanks

This article is helpful reading:
http://www.checkthatcar.com/brake%20fluid.asp
As you can see the older SAE 70R1 is now obsolete. There are some concerns that regulators don't consider older cars and trucks when making changes to things like brake fluid. Materials have changed. However, if you are starting with an empty system, Use DOT4 from any FLAPS. If you have some old fluid in the system, then flush it out with new DOT4. If you just need to top off the system then you could use DOT3 until you flush the system. DOT3 is very close to the old Brake fluid specs. DOT4 has a higher boiling point, and is better. Under no circumstances use DOT5, Never, It is silicone based and is not good for the system in your truck. Now might be a good time to consider changing the flex lines in the truck. If you have put in a new wheel cylinder, or a kit then flushing the system is a good idea. Not hard to do, won't take much time and might save the metal lines from rusting. Others may have some suggestions.

simpler answer, just go to your nearest parts store and get a jug of common Dot 3

Bill

Other thing to remember about DOT3 is that it's hygroscopic (that means it attracts moisture). In my opinion it's a good idea to fully bleed out your brake system about every two years. This keeps accumulated moisture from rusting your lines out from the inside and will firm up your brakes.