Your ideal choice of oil would be an ester semi-synthetic 10W-40 or a 10W-30 that is also shear-stable. The fact that the oil is shear-stable is more important than the fact that it is semi-synthetic. You are still better off choosing shear-stable mineral-based oil than a low-quality semi-synthetic one that isn’t shear-stable. Only for frequent long-distance riders would the cost of a full-synthetic oil be worth it, as it can help save on oil changes and fuel costs.