Viscosity of Monograde and Multigrade Oils - Amsoil

TSB: MO-2006-05-01Date: 05/01/2006Technical Service BulletinProduct Description: AMSOIL 10W-30/SAE 30 Motor Oil (ACD and ASE)Subject: Viscosity of Monograde and Multigrade OilsOBJECTIVE:To explain how certain AMSOIL engine oils canqualify for both monograde and multigrade viscosityratings.TECHNICAL DISCUSSION:Oil Classification SystemIn selecting a proper engine oil, the vehicle ownermust consider both the oil viscosity and the lubricantservice requirements for the vehicle. To enable theowner to identify a proper oil, the vehicle manufacturersand the lubricant industry have developed a lubricantclassification system (1).When automobiles first appeared, attempts were madeto identify motor oils. Viscosity was known to be oneof the most important characteristics of an oil, and itwas simply classified as light, medium or heavy, dependingon its viscosity.When more advanced instruments were made availableto measure viscosity, the Society of AutomotiveEngineers (SAE) developed a better oil classificationsystem. This system, known as SAE J300 (1), wasfirst related to the kinematic viscosity at 100 o C asshown in the following table I.This classification system was used for oil differentiationuntil the late 1960s. During this period of time,the lubricant oils were mostly prepared with mineralbase stocks and had a very limited range of operationtemperature. This led to the development of multigradeengine oils which can be operated in a muchwider temperature range.Table I. Classification of Monograde ViscositySAE ViscosityGrade2030405060Viscosity (cSt)At 100 o CMinMaxLess than5.6 9.3Less than9.3 12.5Less than12.5 16.3Another way to classify the oil is to add the letter “W”behind the number. The “W” stands for winter andindicates that an oil is suitable for use in colder temperatures.The lower the number in front of the “W,”the better the cold temperature protection. This serviceclassification mainly looks at the low temperatureviscosity of the oil. For example, the following tablelists the requirements of the low temperature crankingviscosity at different temperatures:Table II. Low Temperature ViscositySAE ViscosityGradeLess than16.3 21.9Less than21.9 26.1Cranking (cP)Max at temp o C0W 6200 at –355W 6600 at –3010W 7000 at –2515W 7000 at –2020W 9500 at –1525W 13,000 at –10Submitted By: DW/DY Reviewed By: DY Approved By: Alan Amatuzio Approval Date: 5/05/06Distribution: ___Internal X AllPage 1 of 2AMSOIL INC., AMSOIL Bldg., Superior, WI 54880 (715) 392-7101 © Copyright 2006

TSB: MO-2006-05-01Date: 05/01/2006Technical Service BulletinProduct Description: AMSOIL 10W-30/SAE30 Motor Oils (ACD and ASE)Subject: Viscosity of Monograde and Multigrade OilsSAE 20 and SAE 20W are two totally separate monogradeclassifications. SAE 20 describes the high temperatureviscosity of the oil and SAE 20W describesthe low temperature cranking capability of the oil.In order to allow engines to start at low temperatureswhile providing sufficient viscosity at high temperaturesto protect engines against wear, multigrade oilswere developed. An oil can be classified as a multigradeSAE 20W-20 if the oil can meet both the lowtemperature cranking viscosity of 4500 cP at –15 o Cand the 100 o C high temperature kinematic viscosityrequirement between 5.6 and 9.3 cSt.Typically, a type of additive called Viscosity Modifier(VM) or Viscosity Index Improver (VII) is added tothe base oil to achieve multigrade performance.These types of organic polymer additives thicken theoil at high temperatures while having a minimal thickeningeffect at low temperatures. The addition of aviscosity modifier allows for the use of lower viscositybase oils to achieve the cold temperature requirements.The use of light weight petroleum oils increasesoil volatility (burn-off), contributing to excessiveoil consumption and oil thickening.RECOMMENDATIONSAMSOIL ACD and ASE 10W-30/SAE 30 engine oilscan be used in any applications requiring a monogradeSAE 30 or multigrade SAE 10W-30 engine oil withthe performance specifications listed for each product.AMSOIL ACD has a performance emphasis on heavyduty on-road diesels with an API CI-4 Plus rating,while it is also applicable for gasoline engines with itsAPI SL rating.AMSOIL ASE has a performance emphasis on smallgasoline and diesel engines used for commercial serviceor by the homeowner. AMSOIL ASE carries theAPI SL rating for gasoline and API CF/CD rating foroff-road diesels.REFERENCES1. Society of Automotive Engineers, Publication J-300, December 1999.AMSOIL Heavy Duty Diesel Oil (ACD) and SmallEngine Oil (ASE) meet multigrade viscosity requirementswithout the use of viscosity modifiers. This isaccomplished through the use of naturally high viscosityindex, wax-free synthetic oils. These oils meetboth the low temperature requirements of SAE 10Wand the high temperature requirements of SAE 30.Thus the products are true SAE 10W-30 and SAE 30oils.Submitted By: DW/DY Reviewed By: DY Approved By: Alan Amatuzio Approval Date: 5/05/06Distribution: ___InternalX AllPage 2 of 2AMSOIL INC., AMSOIL Bldg., Superior, WI 54880 (715) 392-7101 © Copyright 2006