Just to be clear I use Castrol oils (grade dependent on vehicle) changed at half indicated intervals, genuine coolant and PBR (Australian brand) DOT4 brake fluid changed on BMW intervals. To paraphrase the article (no author) Behr radiators supplied in the USA are prone to AlPO4 (phosphate) coating on the radiator tubes, if the wrong coolant is used. The author also thinks that the standard radiator is on the small side across the range. The BMW coolant is termed G-48 (which means nothing to me; maybe some one else knows). Behr know AlPO4 is an insulator and will cause overheating problems. Brass is not affected. IMO radiator flush compounds do not seem capable of removing the AlPO4 coating. I GUESS that anything that will dissolve the coating will also dissolve the radiator with it, but that is a GUESS. Any chemists out there??
Good - Fast - Cheap: Pick any two.
E23 735i; E32 735iL (X 2 - 1 Alpine White and 1 Glacier Blue); E34 535i; E38 735iL; R50 Cooper; R55 Cooper Clubman.
E21 318i; E30 318i; E32 735iL; E34 535i; E38 730iL; E53 4.4i