Q&A : What Kind Of Oil Does A Lawn Mower Use? & More Questions

What Kind Of Oil Does A Lawn Mower Use? API Service Symbol guide and meaning.
View or download the MOTOR OIL GUIDE document from API.

We answer a range of lawn mower oil questions, such as : What kind of oil does a lawn mower use? Can I use synthetic oil in my lawn mower? What type oil for my push mower? Can you put motor oil in a lawn mower?

Want a quick answer to the type of lawn mower oil you should use? Follow the recommendation of your manufacturer oil which you will find it in the user/service manual. If you don’t have the physical manual, use Google and type “mower brand + model + PDF.” You could also check the manufacturers website for information and answers in the FAQ section or download manuals. It’s that simple. We discuss this in more detail later in the article.

So, why all the hype about special oils and additives, using/not using car engine oil, etc. I’m about to investigate all that and give you straight answers to most of the more common questions people ask.

What kind of oil does a lawn mower use?

Push mower & riding mower…

What kind of oil does a lawn mower use is a popular question, and it unrelated to one type of lawn mower. Owners of push and riding mowers have the same concerns. Anyone who ventures out to buy oil need to understand that all oils are not equal. If you buy the wrong oil it can damage your engine. It applies equally to oil for your vehicle, lawn mower, or any gas or diesel engine.

When buying oil for the lawn mower you will find two rating codes you must consider. The viscosity rating system created by Society of Automotive Engineers (SAE) and the service rating set by the American Petroleum Institute (API):

Viscosity rating of oils (SAE)

What do 10W-30 or SAE 30 and synthetic 5W-30 oil mean? SAE is a numerical code system for grading motor oils according to their viscosity characteristics established by The Society of Automotive Engineers. It shows the viscosity, or thickness of the oil, at a specific temperature, because the viscosity of oil changes with temperature. We call this the SAE, they print it on every bottle of oil and will also show whether the oil is synthetic.

But what is the real meaning of the viscosity numbers on a bottle of motor oil. Viscosity is an oil’s speed of flow through a device known as a viscometer. The thicker the oil is, the higher its viscosity and the slower it will flow.

VIDEO | Understand Oil Viscosity in General

Mono grade oil (SAE 30)

A rating of SAE 30 is a single or mono-grade oil, they only test it at engine operating temperatures of 210°F. An air-cooled lawn mower engine runs at oil temperatures slightly higher than automotive engines. This is because of the better cooling used in those engines,  yet, the recommended oil viscosity is the same for automotive engines and gas-powered mower engines. Manufacturers recommend SAE 30 for most small engines used in mild climates ranging from 40°F to 100°F. Using SAE 30 below 40°F in a lawnmower engine will cause hard starting.

Multi-grade oils (SAE 5W-30)

A “W” in a viscosity rating means the oil viscosity was tested at a colder temperature too. The numbers after the W, (SAE 10W-30) are as tested at 210°F. Which is considered approximately the same as an engine’s operating temperature. Therefore, at 210°F the SAE 30 motor oil has the same viscosity as a 10w-30. It performs the same as an SAE 10 motor oil at the cold temperature but still has the SAE 30 viscosity at 210°F.

The advantage of using a Multi-grade oil like 5W-30 is that the oil flows well when starting the engine from cold. Meaning there is no metal to metal contact. Lawnmower engines do not have the forced oil circulation used in automotive engines. It scoops the oil in the crankcase up with the connecting rod and splashes it into the engine. If the oil is too thick, it does not splash well enough and the components run dry. Causing them to overheat and wear out prematurely.

Multi-grade oils such as SAE 5W-30 and 10W-40 are widely available and used in cars and commercial vehicles. Some small engine manufacturers like Briggs & Stratton recommend synthetic SAE 5W-30 oils for lawn mowers fitted with their engines. Thin enough to flow at air temperatures of -31°F and thick enough to perform satisfactorily up to 86°F. The viscosity you choose depends on where you live, SAE 30 is too thick for Alaska but good for most warm climates.

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An easy way to change your lawn mower oil. (Amazon)

Service rating of oils (API)

The service rating of oils is classified by the American Petroleum Institute (API). It certifies that a motor oil meets certain Original Equipment Manufacturer (OEM) quality and performance standards. On the oil container product label, you will find the service rating in the API “Service Symbol Donut”.

They also indicate the viscosity of the oil in the center circle of the service symbol donut. in the top half of the outer ring of the donut, you will find the API service rating. The API service classification is the two-letter code. The code starts with either an “S” for gasoline engines or a “C” for diesel engines. This is your first important distinction, do not use any oil with an API code starting with “C” in the gas lawn mower! Also, do not put oil with an API code starting with “S” in your Diesel vehicle.

API Certification Mark, also known as the “Starburst”
Make sure the oil you buy has this mark on the label.

The second letter in the API service classification is strongly related to motor vehicles. Yet it is very important as it shows the model years they formulated the engine oil to serve. The first API service classification was “SA”, showing it is suitable for cars built prior to 1930. The API service classification codes following on that first SA code are in alphabetical order, and its current level is API SN.

Oils with a rating of API SA through SD (SA, SB, SC, and SD) has no additives to protect your engine. It may harm modern gasoline-powered engines built since 1971. Only California has laws to prevent the sale of API SA engine oil. You can easily pick up the wrong oil. This classification is your guide and you can ignore names like Premium oil that sound like quality.

Besides an API Service Classification, it may specify an International Standardization and Approval Committee (ILSAC) requirement in your owner’s manual. These include codes such as GF-3, GF-4, and GF-5. ILSAC GF-5 is the latest standard that applies to Multi-grade oils.

This is enough information to enable you to buy engine oil for any of the engines you own, including motor vehicles and farming equipment. You need your owner’s manual to find which oil they recommend for your engine. If you don’t have it, you can find it online, simply type “your mower brand + model + PDF” in Google and your manual should show up in the results. For example, type : “Lawn-Boy 17730 PDF

On the website of The Petroleum Quality Institute of America you will find an excellent pictorial guide indicating the API service classification. It also shows examples of the API donut and other certifications.

How have oil standards changed over the years? View this visual history of API motor oil standards.

What kind of oil does a lawn mower take?

I recommend using SAE 5W-30; it offers the best protection at all temperatures. You will experience improved starting and less oil consumption. When you choose your lawn mower oil, you must make sure you use the API ratings recommended by the manufacturer. I do not recommend special additives; buy the correct oil and change it as recommended and your engine will last a lifetime.

Can you put motor oil in a lawn mower?

Yes, if you have a 4-stroke lawn mower — it’s the same type of oil used in your motor vehicle as you would use in your 4-stroke lawn mower. Although, you must be sure that the SAE viscosity and API codes are the same as specified in your lawn mower user’s manual. YOU MUST REFER TO YOUR MANUAL. Small four-cycle engines and all four-cycle engines need lubrication to keep the moving parts cool and free running.

The oils we use are the same. Do not add additional additives, you will not improve the lubricant. The additives in engine oil are chemical compounds that improve the lubricant performance of base oil. The additives enhance existing base oil properties and include antioxidants, corrosion inhibitors, anti-foam agents and emulsifying agents.

Is your lawn mower a 2-stroke or a 4-stroke engine? This is very important as they both have completely different engine oil requirements. We answer this question late in the article.

VIDEO | How to Change Your Lawn Mower Oil?

Can I use synthetic oil in my lawn mower?

Briggs & Stratton, Honda, Toro, and Kohler recommend synthetic oil in their engines. But you must use standard, 10W-30/SAE 30 or 5W-20/5W-30, the first time you use new or rebuilt engines. It’s used to run in the engine for the first 50 hours of use before switching to synthetic oil. The viscosity mostly recommended for synthetic oil is 5W-30. I still urge you to check the owner’s manual for the SAE and API ratings of the oil.

How much oil does a lawn mower take?

You will find that most small engines need 20 to 24 fluid ounces of oil. The manual will tell you and in the specifications of the engine, they normally show it. Fill the engine slowly and check the oil level as you proceed so you can get a feeling for your progress.

I put too much oil in my lawn mower. What do I do?

Don’t start the engine to see if it will run! You must drain the excess oil just like you drained the old oil, but this time into a clean container so you can use it again. Proceed slowly when you drain and measure periodically till you get it just right.

Don’t put too much oil in your lawn mower

What Kind Of Oil Does A Lawn Mower Use?

What type oil for my push mower?

Read the manual; and if you do not have one, your mower is too old or not marketed anymore, it most likely uses SAE 30. Use API rated oil SJ or better. On the Briggs & Stratton website, they provide a good visual guide to the oil grades. They recommend using SF, SG, SH, SJ or higher. All oil distributors have guidelines available on their websites and literature. Your local lawn mower supplier will also be able to suggest a good oil for your mower. Many push mower manufacturers recommend using synthetic oil in any of their machines after the first oil change and 50 hours of use.

What kind of oil does the Ride-on mower use?

By now you know what the answer is. Find your riding mower user’s manual, skip to the lubrication section and determine what SAE viscosity and API code oils they recommend. If, not, use the internet to find the information or contact your local dealer or small engine specialist. Do not use old engine oil you drained from the farm truck or any other vehicle.

2-stroke vs. 4-stroke lawn mower oil — How are they different?

Two-stroke oil differs from four-stroke oil. DO NOT use a four-stroke oil in a 2-stroke engine and NEVER use 2-stroke oil in a 4-stroke engine.

Four-cycle or 4-stroke engines are the most abundant lawnmower engines. But many lawn mowers, weed whackers, and chain saws use 2-stroke engines. A 2-stroke engine does not have a sump containing oil, it has no oil reservoir. You add the oil directly to the fuel and it burns in the combustion chamber along with the fuel.

Therefore, it must be more refined than 4-stroke oil, and it contains additives like:

  • Detergents to remove varnishes and carbon deposits from the combustion ports.
  • Anti-wear agents to protect moving parts,
  • Biodegradability components and antioxidants.

Four-cycle oil also contains additives, but different. If you run a 2-stroke engine with a 4-stroke oil in the gas, it will damage the engine and significantly shorten its life. 4-stroke oil does not contain the required additives to make it clean burning. It is not what they designed it for. 2-stroke oil is too thin and not designed to withstand the conditions in a 4-stroke engine and will permanently damage the engine.

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