Getting into a freezing car in January is miserable, but waiting until the first snowfall to buy a remote starter means paying peak labor rates and waiting weeks for an appointment. Cars already cost plenty to keep on the road, so timing your add-ons makes a big difference. Early autumn is when specialty shops are slowest and most open to negotiating.
Always nail down the hardware and labor pricing before you talk about how you are paying. Once you settle on a fair total, using an interest-free card window lets you handle the upgrade without draining your monthly cash flow.
A 0% intro rate is a hard deadline, not free money. If you still carry a balance when the 15-month window ends, standard interest applies to whatever remains, so stick to the monthly schedule and clear the charge before then.