Autultery

That sense when you're driving an automobile other than your own (and enjoying it) that you are cheating on your car. This feeling of guilt and cheating intensifies exponentially when contemplating/financing/purchasing a new vehicle and reaches it height as you see your trade-in getting smaller in the new car's rearview mirror.

Dude 1: "Dude! You got that new Jeep! Niiiiiiicce!!!"
Dude 2: "Oh man... I love this car but I feel like SUCH an autulteror."

OR

Woman parks new car all the while avoiding looking directly at old car parked in driveway which she has not driven in awhile (and frankly hasn't missed). She pats it on the hood with a grimace and mumbled apology because she feels like she's committing autultery with the new, nicer car.