Updated: Nov 1, 2021
Most of us decide to put things in our bodies that we probably shouldn’t. When you eat a big huge chili dog with extra onions, you may feel some rumblings in your stomach and reach for the antacids. Those problems in your stomach are a byproduct of consuming something that’s difficult for your body to digest. A similar thing happens in your truck, as some of the byproducts from the combustion of diesel fuel are acids.
When nitrogen from the air and sulfur from fuel combine with water it forms nitric and sulfuric acids that will attack engine metals, causing damage that can eventually result in engine failure.
For the chili dog, the simple solution to indigestion is grabbing an antacid to neutralize the acids in our stomach. In order to combat byproduct acids in a diesel engine however, the manufacturers of diesel engine oil must blend in acid neutralizing detergent additives. The most common ingredients to neutralize acid are magnesium and calcium.
Total BaseNumber (TBN) is the measurement of the amount of these acid-neutralizing additives and is commonly referred to as the “reserve of alkalinity”. New diesel engine oils typically have a starting base number of around 10. It is generally recommended that diesel engine oil be changed or “sweetened” when the base number is 25% of the starting base number for the new oil. For example, engine oil with a starting base number of 10 should be changed or sweetened if the base number drops to 2.5 as determined by oil analysis testing. At a value of 2 the oil becomes acidic and damaging to the engine.
The act of sweetening the oil involves draining 30% to 50% of the used oil and replenishing it with the appropriate amount of new oil - thereby refreshing some of the acid neutralizing additives.
In simple terms, the TBN of engine oil is akin to a “Tums”, used to neutralize acids in our stomach.
If you are running extended oil change intervals, engine oil analysis is a must. Your oil’s TBN is a very valuable factor in evaluating the condition of the oil and helpful in determining when to change it.
Don’t let your truck get terminal heartburn! Be sure to keep an eye on that Total Base Number.