[Banshee]

I don't think a lower temp thermostat would help. I do not believe that the temp difference would be significant. If it made any noticable change, it would be for the worse, however, as you are losing more energy to the cooling system.

IC engines are most efficient running as hot as the materials can stand. (More energy from the hot expanding gas, to push on the piston, rather than it being lost to the cylinder walls, cooling the gas & lowering the cylinder pressure.)

If your engine is overheating, though, a better rad would be the way to go. But if you aren't, then it won't help either.