AMSOIL 100% Synthetic Small-Engine Oil is offered in 5W-30, 10W-30, 10W-40 and 15W-50. AMSOIL describes all four with the same core claims, including “Protects up to 200 hours.” The difference between them is viscosity, which is about temperature and the engine maker’s requirement. For what the numbers mean, see motor oil viscosity explained.
How the grades differ
| Grade | What the numbers tell you | Typical reason a manual lists it |
|---|---|---|
| 5W-30 | Lowest cold-viscosity rating of the four | Cold-weather starting, such as snowblowers and winter generators |
| 10W-30 | A common all-around grade | Many mowers, generators and pressure washers across a wide temperature range |
| 10W-40 | Higher viscosity at operating temperature | Equipment whose maker lists it, often for warmer conditions |
| 15W-50 | Highest of the four at operating temperature | Equipment whose maker lists it for hot conditions or heavy use |
Many small-engine manuals include a temperature chart showing which viscosity to use. That chart, not a general table like this one, is what to follow.
Choosing a grade
- Find the viscosity chart in your engine manual.
- Note the temperatures the machine actually runs in, not just the season.
- Pick the listed grade for that range.
- Check the oil level on level ground, the way the manual describes.
- Do not overfill; it can cause smoking and other problems.
- Change by hours or at least once a season.
- Use the lookup if you are unsure; it lists products for many engines.
Frequently asked questions
Can I use 5W-30 in my mower in summer?
Only if your manual lists it for those temperatures. Many small-engine charts show 5W-30 as acceptable across a wide range, but check yours.
Is 15W-50 better because it is thicker?
No. Thicker is only better when the manufacturer calls for it. The wrong grade can make cold starts harder.
Do these work in a snowblower?
Many snowblower manuals call for a 5W-30 in winter. Check yours, and see the snowblower page.
AMSOIL products for this job
- AMSOIL 5W-30 100% Synthetic Small-Engine Oil. AMSOIL says: “Protects up to 200 hours”; “Helps extend engine life”.
- AMSOIL 10W-30 100% Synthetic Small-Engine Oil. AMSOIL says: “Protects up to 200 hours”; “Shear-stable, high-film-strength formulation fortified with anti-wear additives”.
- AMSOIL 10W-40 100% Synthetic Small-Engine Oil. AMSOIL says: “Protects up to 200 hours”; “Prevents ring and valve sticking while helping eliminate carbon deposits”.
- AMSOIL 15W-50 100% Synthetic Small-Engine Oil. AMSOIL says: “Protects up to 200 hours”; “Helps produce maximum power throughout their service lives, helping you get more work done”.
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.