[wagonman76]

You are exactly right.

And its not only the cooler temperature that reduces efficiency, it takes more of a hit. When below a certain temperature, the car's computer often runs in warmup mode. Which defaults to a richer fuel mixture, and the torque converter does not lock up on an automatic transmission.

I am a mechanical engineer too, and some of my coworkers who have more seniority still dont know jack about cars. Its a different field in a lot of ways.