[Sovereign]

I have a two-option commute in the morning. I can take the highway since I wake up earlier and beat most of the traffic. Or I can take the back roads.

I'm stuck between two logical conclusion, which will only be resolved once I learn which one lies on faulty assumptions.

Take the highway. The engine warms up faster (it's a whopping three miles varying from 40-55MPH depending on traffic conditions). Back roads would never reach operating temperature (four miles) and the engine runs rich the whole time. The engine also is definitely hesitant to shut off (for engine-off-coasting) when it is colder. I've observed this directly.

Take the back roads. The highway forces the car to run rich the whole way at higher speeds.

I know that if I need to run the cabin heat the highway is better because there's no forced-idling-to-heat-the-cabin like there would be at stoplights on the back roads. Unless that's somehow wrong too...