Briggs and Stratton have released their 2025 recommendations for oil, covering both small lawn mowers and riding mowers with the same recommendations.
For situations where the ambient temps to up to 100 F, you can use 30 weight, 10W30 ( with the caveat that oil consumption could increase at temps above 80 F), and synthetic 5w30 ( with no caveat about temperature).
For ambient temps above 100 F there is only one recommendation and that is Vanguard 15w50. It is also the recommendation for continuous use
such as commercial lawn cutting and pressure washing equipment.
They recommend API service SG,SH,SJ
or OR HIGHER.
I took this from their 2025 copy-written document and decided to describe it because there are too many inaccurate recommendations floating out there. This is for Briggs and Stratton equipment.
Also, if someone is actually out there cutting their grass when the ambient temperature above 100 F, have fun.