Car ownership is a series of quiet months interrupted by expensive noises. Beyond the monthly payment, you have to account for the parts that eventually wear out, like tires and belts. Repair shops are usually busiest during the summer and winter holidays, so you often find better labor rates or quicker turnarounds during the spring and fall.
When you hear a high-pitched squeal from the engine, it usually means your alternator or serpentine belt is failing. We use a credit card window to cover these maintenance costs so we can keep our cash for daily expenses. Negotiating the price of the parts is done at the mechanic's counter, while the card handles the timing of the payment.
The interest-free window is a helpful tool for managing a surprise bill, but it is not free money. If you still have a balance after the 15 months are up, the standard interest rate will apply to whatever you still owe.