Originally Posted by Champ
I was helping a friend bleed the brakes on his Aztec today. He ran short of the 5606G he had left from an old can. I had some 5606H & 5606A (plastic screw tops) ordered from ACS for the RV. Both ACS orders were for 5606A but on the older one they sent me 5606H.
Lots of threads/posts on VAF with debate on what’s the best brake fluid to use - don’t want to restart that here. But I am curious as to the difference between A, H, & G. Near as I can tell H & G are classified as “super clean” with no water content and one google reference indicated A was obsolete (although ACS still handle it).
Anyway, can anyone lend more clarity to the differences? Which if any are more appropriate to use in an RV with standard Cleveland 30-9 brakes.
The suffix (A, G, H) just represents the revision of the Mil-spec that the fluid was made to. Rev H. is the most recent version and has been out since 2002 (actual Mil-PRF-5606 is technically an inactive spec. but it's still used for civilian products). There is probably not much difference in the chemical properties of the various revisions of the fluid, but A and G stuff is likely very old. If it isn't in sealed containers, I definitely wouldn't use it.
My opinion is to forget the 5606 and use MIL-PRF-83282 (Royco 782). It's 100% compatible with 5606 but has a much higher flash point meaning it's less likely to result in a brake fire if you have a caliper O-Ring failure.