What properties are you looking for in potentially running a heavier weight oil? In earlier generation engines with greater clearances heavier weight oil was needed to help reduce/prevent piston scuffing/galling. In today's tighter clearance engines oil flow is critical to maintain temperature control in critical areas like bearing surfaces. The main source of bearing failure is high heat which is best dissipated through oil flow moving the heat to cooler parts of the engine oil coolers and etc. Heavier weight oil while maintaining it's viscosity at higher heat flows less volume and thus moves less heat allowing bearings to heat up more and thus have even less clearance and thus even less flow. It might be ok or less damaging in engines with high wear, but otherwise I have the opinion (and it is only that) it is best to stay with the recommended viscosity.
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