Modern cars run higher temps for emissions purposes, not efficiency.
Didn't mean to imply efficiency is the WHY modern engines run hotter, but holding the intake charge constant and increasing exhaust gas temperatures does improve the thermal efficiency of an air-standard cycle.
Thermal efficiency = 1-(Qi/Qe) = 1-(Ti/Te)
Or, looking at it the other way: Holding my engine temp constant (@ 195), my car runs better E.T.s on a cold night in Georgia than on a hot night. (reduced Ti improves thermal efficiency)
OMG, look away! It's an engineering discussion!
Bluedawg
