john smith wrote:

During Winter in the colder climes, do you use less fuel when you fly
because the air is more dense?

First, lift is proportional to mass-air flow over a curved surface.
Cold air is denser so at a give speed, you'll get more lift from cold
air. Now, if you choose to, you can throttle back a bit to get better
fuel economy.

Then, the engine power is controlled by the fuel/air mixture. To burn
X fuel molecules you need Y air molecules. Cold air will supply the X
molecules of air easily.
--Bill