*TBN is Total Base Number. Containment of contaminents is a primary need within an engine. The higher the detergent package or TBN the cleaner the engine. TBN controls excessive wear and deposit formation, providing you less maintenance and longer engine life. TBN costs about .10 cents per gallon for every TBN point in the oil. So be careful with low quotes...it may cost a good deal more down the road.