Honda GX31 Owner's Manual page 6

Use Honda 4-stroke, or an equivalent high detergent, premium
quality motor oil certified to meet or exceed U.S. automobile man-
ufacturer's requirements for service classification SG, SF. Motor
oils classified SG, SF will show this designation on the container.
SAE 10W-30 is recommended for general, all temperature use.
Using nondetergent oil or 2-stroke engine oil could shorten the
engine's service life.
MULTI
VISCOSITY
Ambient temperature
6