Arvid,
You will probably get a mixed reply to your question. There is no reason that 10W-30 will not work well in your engine. It will have the low viscosity necessary to lubricate the piston pin and cylinder walls, excellant anti-wear agents and corrosion inhibitors, and suficient viscosity for valve train, the main and rod bearings. If a single weight oil is used, in the colder weather a 10W or 20W is all that should be used. In hotter summer temperatures up to a 30W is ok. The higher viscosity oils are too high for these engines. :)
