Originally Posted By: m37charlie
The very low TBN is why I'm switching our BMW X5 35d from Castrol SLX Professional OE to Delvac 1 LE 5W30.
It has a TBN>12 despite SA = 1.0%
On my first UOA I had a TBN of 1.5 and a TAN of 4.83 on the Castrol at 10K miles despite a 9L sump.
Scary.
Charlie
Good move, I would've done the same. Though, the 10k OCI ensures the oil SUGGESTED will "woooork".