Total Base Number (TBN)

A key indicator of the remaining life in heavy-duty engine oils. Engine oils are manufactured with a base reserve to neutralize the corrosive acids produced by the combustion process. TBN values, expressed in terms of the equivalent number of milligrams of potassium hydroxide per gram of oil sample (mg KOH/g), generally range from 6 to 80 mg KOH/g in modern lubricants, 7 to 10 mg KOH/g for general internal combustion engine use, and 10 to 15 mg KOH/g for diesel engine operations. A low TBN indicates that the oil needs to be replaced.