About Small Engine Oil

By: Leon Rhodes

Small engines power all sorts of home and garden equipment such as lawn mowers, leaf blowers, chainsaws and grass trimmer. Regular oil changes help extend the life of 4-cycle small engines so lets discuss which type of oil is best and why.

This page is about oil for 4-cycle small engines. For 2-cycle gas oil mixing information visit the gas oil mix chart.

Small Engine Oil Types

Manufacturers typically recommended using SAE 30 oil in their small engines. Thanks to advancements in oil technology you can also use 5w30 and 10w30 oil without problem but there are some exceptions.

For older or worn small engines I recommend sticking with regular single viscosity SAE 30 oil to prevent oil leaking past the piston rings at startup. Multi-viscosity oils can leak through small grooves in the cylinder wall and cause the small engine to burn oil and smoke until it warms up.

For new or rebuilt small engines I prefer 5w30 or 10w30 oil to get a bit of extra protection while the engine is cold.

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).

The Difference Between Oil Types

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(30).

You can use 5w30 and 10w30 oil instead of SAE 30 oil in small engines. The number after the w is the important number and you want to make sure not to use anything less than 30 weight to avoid engine damage.

If you put car oil in a small 4-cycle engine nothing bad will happen as long as you make sure the viscosity rating is high enough, which means at least 30. SAE 30 or any oil rated 'w30' should be OK.

Small Engine Oil Thickness

5w30 and 10w30 have a lower viscosity rating when cold, they are called multi-viscosity oils. 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.

Manufacturers recommend synthetic oil in their small engines but not until a new engine has had at least 5 hours of use. Enough wear to properly seat the valves is needed before switching from regular oil to synthetic oil.

Which Small Engine Oil To Use

The best oil to use in a small engine is always the one recommended by the manufacturer, which is typically SAE 30 or 5w30. Companies such as Honda and Husqvarna offer a house brand of oil to use in their small engines, which is SAE 30 rated.

If you don't have the small engine manual that came with your machine, or you don't have the recommended oil, know that you can use 5w30 and/or 10w30 as a safe substitute and that it's better to change the small engine oil than to wait.

You don't have to use house brand oil in a small engine, in fact you can probably save money with a cheaper but just as effective alternative.

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.

SAE 30 is not the same as 5w30 and 10W30 oil. SAE 30 is a single viscosity oil meaning it flows more slowly in a cold engine. 5w30 and 10w30 oil are multi-viscosity oils, they flow better when cold and provide the same protection as SAE 30 oil when hot.

I use 5w30 synthetic oil in my older small engines and have never had any problems.

Can you use regular motor oil in a small engine?

SAE 30 oil is recommended, however, 5w-30 and 10w-30 will work in small engines. The important thing is the 30 viscosity rating, it represents the operating temperature viscosity required by the engine.

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?

In terms of protecting the small engine from heat damage caused by friction there is no downside. The only reason you may want to stick with SAE 30 oil is when the small engine is worn and oil begins to leak past the piston rings. Thinner oil tends to do this more easily at startup.

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.

Source: I have Over 35 years of experience with small engines, LR. Always consult your small engine manual for recommended maintenance instructions.


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