Most small consumer-grade 4-strokes use splash oiling, not pressurized oiling systems. Multi-vis oils are really tailored for the latter, to speed oil flow when cold. No point in using a multi-vis oil unless you have a commercial-grade engine with an actual oil pump (and likely, oil filter). Some commercial mower engines are set up that way to help them last longer while mowing inclined or terraced lots.
Also, multi-vis oils thin out faster in air-cooled engines. So 10W30 will work if that's all you can find, but small engines generally last longer with the straight 30W (dinosaur squeezings or synthetic).
My Briggs powered lawnmower engine is a pressured unit.
Ditto the Honda motor on our wood splitter.