5W-30 is fine too, as long as you don't experience cold winters:
But I don't see the advantage. The higher the viscosity, the greater the resistance to oil flow. Generally speaking, using higher viscosity oil decreases oil flow rate and increases oil pumping losses, and so provides less oil pressure to the points of lubrication. That's particularly a concern when the engine is started cold, which is when the most engine wear occurs. Plain bearings, such as the ones that support your crankshaft and camshaft, depend on oil pressure and flow rate to maintain film thickness. Another potential downside of higher viscosity oil is that it increases friction between lubricated surfaces that are moving past each other, e.g. a crankshaft spinning in a plain bearing. That increases shearing forces within the oil, which breaks down the oil faster.
But I don't see the advantage. The higher the viscosity, the greater the resistance to oil flow. Generally speaking, using higher viscosity oil decreases oil flow rate and increases oil pumping losses, and so provides less oil pressure to the points of lubrication. That's particularly a concern when the engine is started cold, which is when the most engine wear occurs. Plain bearings, such as the ones that support your crankshaft and camshaft, depend on oil pressure and flow rate to maintain film thickness. Another potential downside of higher viscosity oil is that it increases friction between lubricated surfaces that are moving past each other, e.g. a crankshaft spinning in a plain bearing. That increases shearing forces within the oil, which breaks down the oil faster.