I finally changed the oil on my lawn mower, which is about 10 years old. It had the original blue-dyed Briggs and Stratton branded SAE 30 it came with. Yard Machines lawn mower made by MTD, featuring the Briggs and Stratton 500-series engine, 158cc, 5hp.
I replaced it with SMB-brand 10w30 from the Dollar Tree. It comes in a 16oz bottle, which is perfect for small engine use, and is a synesthetic blend meeting API SN standards.
The original Champion RJ19LM spark plug was replaced with an NGK 5798 (aka BR2-LM). Autozone has the spark plug for $1.95, free shipping, no minimum.
Now the mower starts on the first pull
I don't visit the small engine forum much, but I'm sure some people here have used that little bottle for $1 in their small engines.