TBN is the last 21 for Oil condition in which there are average values decreased when compared to the oil, but it has not yet reached the criteria for BMW4 is still intact, there is a difference in the way that is reduced.
21 TBN is the last in which the average of the Oil condition is reduced compared with oil, but did not reach the threshold for BMW4 remain so, was there a difference in the reduction.
21 TBN is the last value on the part of the Oil condition which means was decreased when compared with the new oil but also ไม่ถึงเกณฑ์ and for BMW4. Remains the same is there is a difference in the lower.