Not to beat a dead horse but i found this on bmwe34m5.com


Subject: M5 FAQ/Coolant
I thought that you may be interested in a post from Jim Conforti that I saved some time ago. He rates the pass and fail brands along with the respective corrosion indexes:

"What are the recommended coolants?

BMW coolant if you want to spend the money, otherwise:
---------------------------
(by Jim Conforti: jec@us.dynix.com)
Zerex 0.1 mg/cm^2/wk corrosion
Award 0.2
Pronto 0.2
Trust 0.3
Pah-Nol 0.4
Texaco 0.4
Recycled 0.6
Prestone 0.7

FAIL:

Crown 8.4
Shellzone 10.2
Peak 11.9 <- this one's sold everywhere...
Fleetline 12.6
UniGard 12.8
Beaver 13.5
MacGuard 15.0
Sure 19.7
500XL 20.0