My lawn mower Briggs engine calls for 30W oil. I have used 10W30 with no problem. I have a leftover bottle of 5W30 that fits no car I own now. Would it be OK for the lawn mower?
Sure!
Once the engine gets hot enough the 5W30 oil has the same viscosity as the straight 30 weight oil.
Tester
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thanks for the helpful, non-snarky reply.
In addition to agreeing with @Tester, I personally use 5W30 in a 1997 model B&S engine that has had a LOT of use. No problems.
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Is the 5W-30 oil you are going to use synthetic? I had an old mower that the manual called for 30 viscosity high detergent. I noticed that 10W-30 synthetic oil was only $1 more than straight 30 weight. I took a chance and spent my Social Security check on the more expensive synthetic oil. The mower had been burning oil so badly that I fogged for mosquitoes as I mowed. I wore a face mask when I mowed and this was before COVID. The 10W-30 synthetic cut the oil consumption by 80%. I no longer needed to wear a face mask when I mowed and only wear the face mask when I go to the bank to get cash. I got three more years use from that mower.
If your mower isn’t using oil, it won’t matter whether the 5W-30 is synthetic or not synthetic. It won’t hurt your mower and might even be helpful.
I am now using my backup mower that I bought in 1988. It has a Tecumseh engine. I use whatever oil I have around. When I changed oil for the mowing season, I had some 30 weight heavy detergent. It didn’t completely fill the oil sump, so I topped it off with 10W-30 full synthetic I had. I have used the mower about 8 hours this session and the oil level has remained constant.
As long as the upper number is 30 or higher on multi-viscosity oil, you will be fine.
I used to run all my Briggs engines on 5W30 synthetic because I used some in the winter months and I had a lot of that grade around the house.
It took DECADES for the Briggs and Stratton engineers to finally accept multi-weight oils.
the jug in question is 5W30 dino, but I plan to buy 10W30 syn for it in the future.
Little or no smoke despite 20 yr age.
I use 5w30 in all my small engines, winter or summer, but I use synthetic. That is according to the revised Briggs recommendations. I guess I wouldn’t worry about it but I have recycled unused oil that I don’t use anymore.