Driving Me Up a Wall: (Yes, But in What Gear ?)

Normally, I can take suggestions from people regarding how to go somewhere. I prefer to set GPS in my car and follow the instructions. Sometimes, the directions are skewed, and adjustments need to be made. I get around in a stick shift in America and have had few problems with it. I have NEVER had issues with the clutch.
Recently I was hosting an Australian pen pal and we had planned a trip from the Southland to the Bay Area; which is basically from Los Angeles to San Francisco.
Whenever we would reach a grade, he would announce to me what gear I needed to be in. What's more, he would also fiddle with the air conditioning buttons with the claim that less usage would provide greater power to the motor. Normally, such comments are taken in stride or accepted with a thank you. His were actual commands and he became irritated if they were not followed immediately and as prescribed. To make matters worse, when he rang up his husband, he told the man about his helpful hinting and how I had reacted to his instruction.
The things you learn from pen pals that you hadn't known throughout the years!