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Understanding lubricant specifications
Learn what viscosity grades, specifications and additives mean when choosing oil. Check your equipment manual and the current product directions before you buy.
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Viscosity and temperature
SAE means Society of Automotive Engineers. Its viscosity grades describe oil behavior under specified conditions; they do not identify every performance requirement. A nearby grade is not automatically an acceptable substitute for the one required by the equipment.
Base oils and additive systems
A finished lubricant combines base oils with an additive system. Those ingredients are designed to work together; a single ingredient or a higher additive concentration cannot establish that the complete product suits an application.
Specifications and approvals
API is the American Petroleum Institute; ILSAC is the International Lubricants Standardization and Approval Committee. Their categories describe defined performance requirements. An equipment manufacturer's approval, an industry license and a lubricant maker's application recommendation are different statements: check which one your manual requires and what the exact product actually documents.
Operating conditions
Short trips, extended idling, towing, load, heat and storage can change the service demands on oil. Use the applicable normal or severe schedule and product limits for the actual operation. Harder use does not by itself justify a different viscosity or an extended interval.
Filtration and oil analysis
Filters and laboratory analysis answer different questions. A filter must fit the system and have an appropriate service plan; analysis reports the condition of a sample. Neither can turn an unsuitable lubricant into the correct initial choice.
How to choose a lubricant
Identify your equipment, check its required viscosity and specification, and use the matching product guide. Read the current product directions before ordering.
What to check before you buy
Record the component, required viscosity, specification or approval, capacity and service conditions. Use the exact product's current application information to check that list; use oil analysis later to evaluate condition, rather than to establish initial compatibility.
Common questions
Does the same viscosity make two lubricants interchangeable?
No. The application, specification, approval, product instructions and component design also control selection.
Is more additive always better?
No. Additives are balanced as part of the complete formulation; suitability comes from the product's supported application and requirements.
Does oil analysis select the lubricant?
No. Choose the correct oil first. Analysis then helps you check its condition while it is in use.
How often should I change the oil?
Follow your equipment maintenance schedule and the oil's current service instructions. Check the limits for your operating conditions.
Optional account programs
Buying for repeat personal or business use?
Review official AMSOIL program information after you have found the products you need.