Motor oil for my lawn mower

Cleaning out my dad’s garage, he offered me some unused motor oil. They have various grades such as SAE 20W-50 and 10W-40.

I use the recommended SAE 5W-30 I my walk-behind Toro mower; it has a B&S 6.75 hp 190cc engine.

My questions are these:

  1. Can I use the SAE 20W-50 and 10W-40 oils in my lawn mower without damaging it?
  2. If I can, what precautions should I take? (aside from checking the oil level more frequently)

Looking forward to any help one can offer.

I would blend it in at no more that 25% with the recommended oil.

Go to the Toro owner’s manual or the Toro website and see what they say. The Toro manual or website might offer the oils you describe as options, but if they don’t I wouldn’t do it.
Even in a small engine oil proper lubrication is critical to the engine’s survival. It isn’t worth risking seizure just to save a couple of bucks.

Can you use it?

Should you use it?

When you consider how little oil is contained in that engine’s crankcase, it is vital that you use only the viscosity specified by the mfr.

I agree with VDC driver

I noticed Stan stated " do I need to check oil more frequently" I check the oil on my mower every time and clean the filter before I start it. I hope he does the same thing.

No you can’t. Go to the Briggs web site. Toro will have nothing for you. Briggs now allows the use of snthetic 5-30 year around for all their engines so I’m now in the process of trying that. I don’t think they have ever said these weights were ok. Odd ball oils that I have end up just going in the recycling containers. My loss, big deal. Our county recycler has a free exchange for stuff like this and paints and so on. They take it all and mix it together so if you like funky tan you can get a lot of it for free.

I have no doubt that any motor oil certified by API and in the recommended weight be should all that is needed to make your motor run as long as don’t tire of it. The amount of oil is minuscule compared to a car, often with out a filter. Why mess around for a minuscule savings ? But, I have no doubt that the frequency of oil change is just as important and if you used this gift oil and changed it twice instead of once a year, it would be fine. But I STILL would Use what is recommend in the cheapest oil you can find and it might cost less then $5 per year.

Take the gift oil and donate it to someone who has a waste oil furnace.of course, I would use it as a rust preventative measure but you can do what you want. Once in a while, I treat my lawn mower to Kubota tractor diesel motor oil or synthetic oil I use in the winter when I have enough of it lying around. IMHO, it’s desert for the lawn mower where I normally just use regular oil.

Although I have always used the recommended 30 weight oil in my mowers, I have one old walk behind mower that really burns a lot of oil. If I had the unused 10W-40 or 20W-50 oil for free, I might be tempted to use it in this mower. I replaced the short block some years back and I don’t think I want to put any more into a mower that I have used 23 seasons. The mower has twin blades–a longer blade and a shorter blade mounted on the motor shaft. I can no longer find parts for this mower, so I have had to improvise. I now use it for mulching leaves in the fall since it does a superb job at this task. I have an even older Toro walk behind mower that I bought in 1988. It hasn’t seen as much use and doesn’t use oil, so I will stick with the recommended viscosity for that mower. I think it pays to buy a name brand mower. The lower part of the handle broke due to metal fatigue on the Toro and I went on an internet mower parts site and found the replacement handle is still available. It was delivered just today.

…great on salads too!!!

I think the discussion about motor oil for lawn equipment is a little too deep in the specifics. The engine was designed around World War II when motor oil was barely recognizable as fresh engine oil by today’s standards. The design is very very low tech and very very robust. These things will run forever on spoiled gas and waste oil.

Pour whatever oil you have laying around the garage in it and change it whenever you remember to and the Briggs will run forever. Put the little bugger into ecstasy by giving it a quart of synthetic oil but never pour race gas into the tank. It won’t like the high octane.

“Pour whatever oil you have laying around the garage in it and change it whenever you remember to and the Briggs will run forever”.
I’ve seen two lawn mower engines throw a rod through the block when 10W-30 was used. This was 20 years ago or so. Back in the 1950s, I put 10 weight in a lawnmower engine and it seemed to be overheating. The thicker viscosity is needed in the air cooled engines to keep them running cooler. The 10W-30 back then would not maintain the 30 viscosity. I am sure the synthetic multi-viscosity would be fine.
I have purchased a Briggs and Stratton tune up kit for my mower which included a new spark plug, air filter and a bottle of “genuine Briggs and Stratton small engine oil”. I noted that this oil was 30 weight. My guess is that it is no different than any other brand of 30 weight oil on the shelf–Briggs and Stratton does not make its own engine oil.

I’ve never used straight 30 weight in any of my Briggs motors, ever. I use whatever multi-weight I’ve got laying around which in the past 25 years has been synthetics. I’ve never had a mechanical failure for over 30 years in any Briggs motor. I’ve got a 50’s vintage Briggs on a generator that sits without service for years on end that still starts when needed. They are not fuel efficient, they are not powerful but they run and run. I can’t even guess how a rod exited the engine block on any multi-grade oil. Briggs engineers still want you to uses 30 weight but they didn’t even design the current crop of OHV engines, Generac did, and sold them the design.