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5-W30 vs 10-W30 oil

Going to change the oil in my lawnmower myself. Per the user manual it specifies:
SAE 30 detergent oil with API classification SF, SG, SH, SJ, SL or higher.

At the hardware store I found multiple oil brands that fit the criteria. Some are SAE 5-30W, some SAE 10-30W, and one that simply says SAE 30. All meet or exceed the API classification.

I’m confused. And I can’t get any employee to help me. They see a man that came in behind me and go to him despite my asking for help. The normal treatment of an older woman shopping in a hardware store. So am asking you wonderful gentleman who have always been kind and courteous.

If it makes a difference to know, the lawnmower is a Toro model 20334.

…still reading, still learning

I would use the SAE 30, since that is what it specifies.

The only case in which I would use 10w30 is if you are dealing with temperatures down around freezing.
Not likely in July.

It’s simple.

The number before the W is the Winter weight of the oil.

So the oil will flow like the weight of that oil down to zero degrees, so it doesn’t get too thick and starve the engine of oil during a cold start.

The number after the W is the weight of the oil once the engine reaches operating temperature.

All the small engines I run (summer/winter) have 5W30 oil in them.


At Ace Hardware they have 30 w marked Lawnmower oil but any 30 w will work.

My old Toro mower specified SAE30 only and said to not use 10W30 multiweight. My new Honda specifies 10W30, so go with your manual, get the one that says SAE 30.

There’s no such thing as a 30W oil.

The oil will either be 5W or 10W.


Then how did I purchase a bottle that is marked SAE 30 W Lawnmower Oil?

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One of the rare times I would disagree with @Tester, his advice is usually spot on.

Here is a link to 30W from Lowes, others have it also.

Marnet, you can get that oil at Wallyworld and if this Toro dies look at battery powered .

Edit: If you are doing a complete change the old oil can be dropped off at most Wallyworld’s that have a vehicle service dept.

Thank you for all the replies! It does help. :grin:

I’ve never looked for a 30-40W oil for any of my small engines.

I want all the protection during a cold starts with my small engines just as I would with my vehicles.


I use 10W-30 full synthetic oil in both my mowers. One mower is a 1992 Homelite-Jacobsen with a Briggs & Stratton Quantum engine. It was the mower I used most often and it began really burning oil. As an experiment, I bought a quart of full synthetic oil under the RK brand name at my local Rural King farm store. It was $2.79 a quart–$1 more than RK straight 30 weight at $1.79 a quart that I had been using. That was the best $ 1 I ever spent on that mower. It bought me two more seasons of use – it rrduced the oil consumption by 75%. This season, however, it began burning oil again.
Our other mower is a Toro 18" mower made in 1988 with a Tecumseh engine. Since it is narrower than the Homelite-Jacobsen, I didn’t use it as often. Since I had such good results using 10W-30 full synthetic in the Homelite-Jacobsen, I have been using the full synthetic 10W-30 in the Toro instead of straight 30 weight as called for in the manual. The Toro wasn’t using oil, but I think the full synthetic gives a little extra protection to the engine. If you go to a multiviscosity oil, I recommend the full synthetic 10W-30.
As for the battery powered mower suggestion, go with a new mower with a lithium-ion battery. I bought a used Black and Decker CMM 1000 from a friend. I put new batteries in the mower and the batteries only lasted two seasons. I replaced the batteries at the beginning of this season for $68. I mowed two rounds and the mower quit. I jumped the switch with a screwdriver and the motor started. I haven’t had time to tear into the circuit board and find the problem. This mower uses lead acid batteries. Mrs. Triedaq likes to mow and I thought the Black and Decker would be convenient for her. Unfortunately, is heavier than the 18" Toro and harder to push, so she didn’t like it. I liked it when it ran, because it was quieter than the gasoline mowers. I may go to a new mower powered by a lithium-ion battery and if it works out, sell my old mowers at a yard sale.

My daughter got an EGO 58V self propelled to replace her Toro self propelled. Since she broke her foot, I have been mowing her lawn for her. The EGO is far superior to the TORO, you will love it. The Ryobi 40V self propelled would be a good choice for small yards but it has to be ordered at Home Depot where the EGO is in stock. Ryobi does have the best yard tools like trimmers, edgers etc in their 40V line. I have spent a good part of today cutting up a 100’ Oak (felled last week by a pro) with my 40v Ryobi chain saw.

@keith I am seriously considering not only replacing my lawn mower, but my leaf blower as well with one powered by a lithium-ion battery. My wife bought me a Ryobi string trimmer about 12 years ago. It uses a lead acid battery. It needed a new battery this year and a new battery is $65. I bought a new Worx string trimmer for $100. It’s much lighter than the Ryobi since it has a lithium-ion battery. I am almost.convinced that for me, lithium-ion battery powered outdoor equipment is the way to go.

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Even the most recent Briggs & Stratton engines that I have serviced for friends had factory recommendations for straight SAE 30 oil when the temperature was above 40*F. On my own engines I have used 15W-40 synthetic for several years after a bulletin was issued re flat tappet wear from various API SM and SN synthetic oils. Everyone has a preference and for the most part those with a preference service their engines regularly and have no problems with poor lubrication.

I can say for sure that 0-20 oil in an air cooled engine will not work. I had filled several engines with that oil in order to periodically start them over the winter and in the spring I made a few passes on my yard on a Snapper and began to hear a tapping and saw white smoke. Of course I changed the oil and there has been no problem with that engine internally since… FWIW that’s the engine that I replaced the carburetor on a few weeks ago and posted here about it. It’s 15 years old and running great.

@Tester has it correct. There is no such thing as 30W oil. It’s SAE 30. Lowes description has it wrong in calling it 30W. If you look at the illustration the bottle says SAE 30, not 30W.

Kind of nitpicking a little. We all know that you don’t need a thing to heat water that is already hot but if someone says they need a new ’ hot water heater ’ it is understood what they mean.

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Pick them nits!
Nit-picking. Q From Tim Nagle: What is the origin of the expression nit-picking? A The phrase comes from the task of removing the tiny eggs of lice (nits) from someone’s hair and clothing, a tedious activity that required close attention and care.

Long ago I recall buying 20W oil and just now searched “30W engine oil” and found that several brands SAE 30 oil was eagerly thrown up. Mac Flecknoe referred me to Jim Cantore.

@Marnet. Your lawn mower calls for an SAE 30 detergent so look for one that is grade SAE 30 HD. Avoid anything that says SAE 30 ND as that is a non detergent. Any SAE 30 that meets SF or higher will be a detergent oil, IIRC SAE 30 ND will have an API classification of SA.

SAE 30 is a single grade oil. The ones that are 5w30 or 10w30 are multi-grade oils. Multi grade oils are for motors that are used all year round where the single grade oils are for seasonal use, i.e summer only.

Edit: single grade, multi grade also known as single viscosity and multi viscosity and occasionally called single weight and multi weight.