Brian, different octane fuels don't burn "hotter" or "cooler". The higher the octane, the more resistance to detonation, which is mostly because of how fast or slow they burn, not how hot. Temperature and pressure remain constant, but speed of burn varies between octanes. Information police alert....

olice:
Any decent modern spark plug
should be able to ignite a complete combustion event with 93 octane fuel in any vehicle. Now, if you used race gas or something over 100 octane you might not get complete combustion, but I honestly never see 93 not burning fully in a modern engine with good plugs and compression.
What is the compression ratio on our 3.4's anyway? Sorry this is way OT.