I've got a 2012 M3 E93 with 48k miles on it, bought used 3 months ago. I changed the oil right away with 10w60 castrol supercar and burned about 1 L of oil in the first 1000 miles of the oil change (within BMW's oil burn rate standards for the M3).
The car runs well and at the 1000 mile mark of the oil change I went on a 2000 mile road trip, including a large section of California's highway 1, driving the car hard most of the way. Before leaving on the trip I added about 10 ounces of distilled water to the coolant reservoir to bring it up to level - and I noted then that there was a small amount of white / yellow stringy mucous-like substance at the top of the reservoir. I attributed it to someone in the car's past putting in off-brand coolant.
Now returned from the trip, the coolant level hasn't budged. The same amount / quality of mucus sludge is in the reservoir (floating atop normal looking coolant). The burn rate of oil is ~0.5 L for the 2000 mile trip.
Thoughts on the source of the mucus sludge? My reading tells me it ranges from bad or wrong coolant to a blown head gasket.
Thanks all - 1st post.
Kevin
