Your owner’s manual lists a viscosity grade and one or more performance specifications. The bottle needs to show both. The front label usually shows the product name and viscosity; the back label lists the specifications and directions. For what the numbers in “5W-30” mean, see motor oil viscosity explained.
What to look for
- Viscosity grade (SAE): for example 5W-30. Match it to the grade in your manual for your temperature range.
- API service category: letters such as SP for gasoline engines or CK-4 for diesel engines. Newer categories are generally written to cover older ones, but check the manual.
- API donut and ILSAC starburst: symbols that show the oil is licensed to a given standard. Not every oil carries them; specialty and racing oils often do not.
- Equipment maker specifications: some manuals require a specific manufacturer approval. The back label lists approvals or says the oil is “recommended for” certain specs.
- Small-engine and powersports standards: 2-stroke oils list JASO or ISO grades, and many motorcycle oils list JASO MA or MA2 for wet clutches.
- Directions and cautions: drain-interval guidance, handling and disposal.
Bottle-to-manual checklist
- Find the viscosity and spec in your owner’s manual first.
- Match the viscosity grade on the front label.
- Match the performance category on the back label or symbol.
- Check for required approvals if your manual names one, especially under warranty.
- For motorcycles, confirm the wet-clutch rating if your bike shares engine and clutch oil.
- For 2-stroke oil, confirm the JASO or ISO grade and the mix ratio.
- When in doubt, use the AMSOIL lookup, which lists products by vehicle and equipment.
Frequently asked questions
What does the “W” in 10W-30 stand for?
Winter. The number before the W relates to cold-temperature performance; the number after relates to viscosity at operating temperature.
Is an oil without the API symbol bad?
Not necessarily. Some specialty, racing and heavy-duty oils are not licensed for a given symbol. Make sure the oil meets what your manual requires.
Can I use a diesel oil in my gasoline engine?
Only if the bottle lists the gasoline category your manual requires. Many diesel oils are not licensed for modern gasoline engines.
AMSOIL products for this job
- AMSOIL Signature Series Max-Duty Synthetic Diesel Oil. AMSOIL says: “Maintains proper viscosity (thickness)”; “Excels in extreme temperatures”.
- AMSOIL OE 100% Synthetic Motor Oil. AMSOIL says: “Delivers 100% synthetic engine protection for advanced automotive technology, including turbos and direct injection”.
- AMSOIL Signature Series 100% Synthetic Motor Oil. AMSOIL says: “Protects – Ultimate long-life anti-wear protection”; “Adapts – Responds to changing conditions”.
Product wording above is quoted or summarized from amsoil.com. Read each product’s label and data sheet for directions.
Use AMSOIL’s official lookup guide to see what is listed for your vehicle or equipment, then order online whenever it suits you.