66 Oil System Sulfur Level and TBN Oils are available with different levels of Total Base Number (TBN) to counteract high sulfur levels in fuel. TBN measures an oil’s alkalinity and ability to neutralize acid. Normally, the higher the fuel sulfur, the higher the TBN is needed. Sulfur creates highly acidic pollutants in the oil that break down the additives at a higher rate. The sulfur content in low-sulfur fuel has been regulated to a maximum of 0.05% by weight for No. 2–D diesel fuel. For fuels that have a sulfur content of 0.5% by weight and above, Volvo Trucks North America, Inc. recommends that oil change intervals are cut in half so a shorter mileage is run between oil changes.
Oil Additives CAUTION Extra oil additives must not under any circumstances be added to any oil used. A shortened engine life may be the result. Using oils to the quality standards recommended in this manual makes the use of extra oil additives unnecessary, as these oils already contain a balanced treatment of additives. The use of extra oil additives such as break-in oils, top oils, graphitizers and friction reducing compounds are not necessary and can even be harmful to the engine.