"Not only can mixing tires degrade the stability of your vehicle, but it affects your tread wear too," says Andrew Gorman, Dufferin Motors & Tires, Alliance Tire Professionals. "As the tread on a tire wears, the tire has less traction and therefore control over your vehicle. If all-season tires are used year-round, the tread will wear down faster. Since winter tires are to be used during the winter season only, there is less wear and tear on both sets of tires."
Tire Technology: The tire technology of winter tires versus all-season tires is very different. In addition to the differences in the rubber compounds mentioned above, winter tires also have tread patterns and sipes (small grooves that cross larger tread blocks) designed specifically to push water aside and dig down through snow to the road surface, maximizing your ability to start, turn and stop. It's important to note that tires marked with the pictograph of a peaked mountain with a snowflake meet the Rubber Association of Canada's snow traction performance requirements.
Once you have your four identical winter tires installed on your vehicle, don't forget to properly maintain them. Checking your tire pressure is just as important in the winter as it is in the summer. For every five degree drop in temperature, your tire loses an average of one pound of air. Proper inflation will prolong the life of your tire and improve fuel efficiency. Air pressure should be checked monthly, especially after the first frost.