I'm with most of the users on this forum. I've used an ice box for most of my travels. Wrapping it in a damp towel during a hot day works wonders - kinda like a Zeer pot. If you go the extra mile and insulate a compartment with 2-inch foam, you can get a 5-lb bag of ice to last 1-2 weeks!
Here's the thing to remember about every "normal" fridge: it has to vent heat somewhere, usually in the teardrop. So running an exhaust fan while using the fridge should help with the fridge performance if the air inside is warmer than the air outside.