5w30 vs 10w30 Lawn Mower Oil (Is SAE 30 Better?)

Regular oil changes help extend the life of 4-cycle small engines, but which type of oil is better to use in a lawn mower?. This article discusses the pros and cons of SAE 30 vs 5w30 vs 10w30 lawn mower oil.

Manufacturers strongly recommend using SAE 30 oil in their small engines. Additionally, there may be a warning in your lawn mower manual describing how 5w30 and 10w30 oil can void the lawn mower warranty.

So what’s the deal? Well, in certain conditions a multi-viscosity oil, such as 5w30 and 10w30, can leak through small grooves in the cylinder wall and cause a small engine to burn oil until it warms up. (Sometimes, more on that below).

SAE 30 vs 5w30 vs 10w30 Lawn Mower Oil

The biggest difference between 5w30, 10w30 and SAE 30 oil is how well they flow when cold. When hot, all three oil types provide the same viscosity protection rating (30).

Synthetic Blend Motor Oil
Synthetic Blend Motor Oil

The difference between SAE 30, 5w30 and 10w30 oil is that 5w30 and 10w30 oils are multi-viscosity and will flow better when cold. Once the small engine is hot, all three oil types provide the same level of protection.

About Small Engine Oil Thickness

5w30 and 10w30 have a lower viscosity rating when cold. This means a cold start with SAE 30 is slightly harder on a small engine than a cold start with 5w30 or 10w30 oil.

Engine oil that flows more freely can coat and protect engine components better when they are still cold, thus reducing wear and tear on your small engine. The trade-off is that they can also leak through oil rings into the combustion chamber more easily, especially in worn engines.

The major small engine manufacturers recommend synthetic oil in their small engines, but not until a new engine has had at least 5 hours of use. A small amount of wear is required before switching to synthetic oil so that the valves can properly seat and prevent leakage.

Which Small Engine Oil To Use

The best oil to use in a small engine is always the one recommended by the small engine’s manufacturer, which is typically SAE 30. Check the manual for your particular mower brand to be safe. Companies such as Honda and Husqvarna offer a house brand of oil to use in their small engines, which is SAE 30 rated.

You don’t have to use house brand oil in a small engine, in fact you can probably save some money with an alternative of the same type.

The reason companies offer their own brand of oil for their small engine, besides profit, is to control oil quality. Advancements in oil technology have mostly taken care of the problem of low quality oil.

Can you use regular motor oil in a small engine?

SAE 30 oil is recommended and should be used, however, 5w30 and 10w30 motor oil is better than using extremely dirty oil, or no oil at all. Just remember to replace it as soon as possible.

Is SAE 30 the same as 10W30?

Not entirely. SAE 30 oil has a 30 viscosity rating when the engine is cold, and so it may flow a little more slowly at first. 10w30 starts with a 10 viscosity rating when cold and gradually becomes 30 viscosity as it heats up, it is a multi-viscosity oil.

Can I just add oil to my small engine?

If your small engine is low on oil, and you don’t have time to give it a proper oil change then yes, adding fresh oil before using the small engine is a good idea as it may prevent engine damage. Just remember to change the oil and give your small engine a tuneup soon after.

What is the downside to using 10w30 instead of SAE 30?

When a small engine is worn oil may begin to leak past the piston rings. Thinner oil, like 5w30 and 10w30, tends to leak more easily at startup. Stick with SAE 30.

When should I change my small engine oil?

Most small engine manufacturers recommend changing the oil at least once per season or after every 50 hours of operation, whichever is less. Clean oil is the most important factor in making your small engine last.

Should I run my small engine before changing the oil?

Yes, running the engine to bring it up to operating temperature, which typically takes 15 minutes, is a good idea before changing the oil. Warm circulated oil will drain better and remove contaminants that would otherwise sit in the engine.

What’s the difference between 5w30 and 10w30 oil?

The difference is how well they flow at startup when the engine is still relatively cold. This means both oils will have the same viscosity rating when hot, but the 5w oil will flow more easily when cold.

I recommend sticking with regular single viscosity SAE 30 oil to prevent oil leaking past the piston rings at startup.