i wouldn't if i was you 10w40 is not to great for cheep mowers 15w40 would really make the engine work before its lubricating starts, which by then the engine could have damage to it and would need replaceng.
the saying of any oil is better than no oil is not true as the wrong oil can do just as much damage to an engine oil pump as old or no oil can
we only advise sae30
you should be able to pick this up at you local mower shop
is the sae 30 fully synthetic?
It says in the Briggs&stratton vangaurd manul that synthetic oil meeting ILSAC GF-2,API certificationmark and API service symbol with "SJ/CF energy conserving ratting or higher is an acceptable oil at all tempratures.
would 10W30 fully synthetic castrol bike engine oil with these certificates be a good all round oil?