As per Mike Miller
The factory coolant change interval used to be every two years. Starting in the late 1990s, BMW lengthened the coolant change interval to every three years, then every four years. As of 2004, BMW says coolant is “lifetime fill.” There was no discernable change in original BMW anti-freeze during this transition, other than who pays for the service during the warranty period.
I recommend changing engine coolant at two-year intervals, using only factory BMW anti-freeze mixed 50-50 with distilled water (reason – BMW anti-freeze is phosphate free, phosphates cause aluminum oxidation, which blocks cylinder head coolant passages and causes head gasket failure, others may claim to be “aluminum safe” or “phosphate free” – make your choice, but I’ve used BMW anti-freeze exclusively in many cars and have never had an aluminum oxidation or head gasket problem)
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