Any tips of suggestions for brand/type of coolant?
E39 Engine coolant: phosphate free (for Europe's high-mineral-content water), amine & nitrite/nitrate free (for USA long-life requirements), & low-silicate or silicate free (for Japan requirements) 50:50 mixture of ethylene glycol & water (the Bentleys say distilled water (Bentley 020-11), aka de-mineralized or de-ionized water, some call it purified water, and the BMW AG TIS 12.11.2007 18:56 specifies water with a pH from 6.5 to 8.0, maximum total hardness of 3.6 mmol Ca++/liter, maximum chloride content 100 mg/liter, and maximum sulphate content 100mg/liter; interestingly the BMW TIS says "potable tap water usually fulfills these requirements". EPA reports show San Jose & NYC tap water easily fulfill these requirements. The BMW TIS expressly states additives are not helpful and are not recommended. BMW lists a score of recommended coolants in their BMW AG TIS 12.11.2007 18:55 which meet the BMW N 600 69.0 standard, some of which are BMW PN:220.127.116.117.454 1.5-liter; BMW PN:18.104.22.1680.316 1 gallon; Castrol Anti-Freeze NF; BASF Glysantin Protect Plus G48, & Havoline AFC (BD04); but most of which are not easily found in the USA. Many Bimmerfesters recommend BMW coolant; however other Bimmerfesters recommend Prestone Extended Life 5/150, Valvoline Zerex G-05, and Service Pro Universal Formula. Others (e.g., chiefwej, aioros), have tested Evans NPG+ but be aware propanol entails a different maintenance philosophy than the aqueous fluids listed above and is not compatible with them. [Total Volume: 1997 I6=10.5 quarts (2.6 gallons), 1997 V8=12.0 quarts (3.0 gallons), 1998-2002 I6=11.1 quarts (2.8 gallons), 1998-2002 V8=12.7 quarts (3.2 gallons), 1997-2002 V8 with latent heater=13.5 quarts (3.4 gallons)]. Prestone says the only reason for phosphate free is the extremely high mineral content of water in Europe - and that in the USA, it's not needed. Replacement Interval: Every three years (Bentley page 020-9) or every four years (aforementioned BMW AG TIS) starting from date of manufacture (except for M-Power vehicles which have 3-year intervals). Note: Mixing BMW-recommended coolant brands is permissible; but mixing types is not permissible unless it's an emergency.