The higher the octane = the level of resistance to detonation (pre-ignition/knocking). It is not an indicator of "stored power" within the fuel. I couldn't find it, not enough time before work, but I think diesel fuel has an octane rating well over 250 (try burning that in your engine though).
Like travisdecpn discovered, higher octane fuel burns slower, so in a vehicle designed for 87, the higher rated fuels likely will not completely burn off, and may cause multiple issues, one being a loss of actual power from incomplete combustion along with increased amount AND rate of accumulation of combustion chamber, cylinder head and valve carbon deposits which also robs the engine of even more power and efficiency.
As for your ticking sound. Is it constant? Does it speed up with engine rpms? Odds are that it is, like mentioned, a fuel valve. My camaro had an electronic, fuel-metering, needle valve that sounded A LOT like valve/lifter tick. You can double check with the dealer to set your mind at ease. BTW, your car was designed to use 0W20, I wouldn't suggest going thicker unless you live in a hotter climate (basically the southwest in the summer).