Recently I had a small leak around the side of one of my car tire which unfortunately  cannot be repaired (because any patch will be push away by the inside pressure of the tire). When I went to the tire store to buy a new replacement tire, I was told unless I can find an exact tire with the same brand and thread pattern, I must replace all four tires together. Otherwise using a different brand or pattern tire will cause damage to the differential gear mechanism of the car. I verified this fact on wikipedia and had to spend four times the expected cost of a tire to make this simple repair - a fact no one told me about all wheel drive cars.

Convenience comes with a potential large cost!!!