Yes, not replacing your spark plugs after 50,000 miles can potentially cause problems in your car's performance. Spark plugs are responsible for igniting the air-fuel mixture in the combustion chamber of the engine. Over time, the electrodes on the spark plugs wear out, which can result in decreased fuel efficiency, misfires, and engine performance issues.

If the spark plugs are not replaced at regular intervals, they can become fouled with carbon deposits, affecting their ability to generate a strong spark. This can lead to poor combustion of the air-fuel mixture, resulting in reduced power, rough idle, difficulty starting the engine, and even engine misfires.

Furthermore, worn or damaged spark plugs can put additional strain on other ignition system components, such as the ignition coils. This can lead to premature failure of these components and further deterioration in the performance of your vehicle.

Regularly replacing your spark plugs as recommended by your vehicle's manufacturer (usually between 30,000 to 100,000 miles, depending on the type of spark plugs used) helps ensure optimal engine performance, fuel efficiency, and overall reliability. It is always a good idea to consult your vehicle's owner's manual or a professional mechanic to determine the best maintenance schedule and type of spark plugs for your specific car model.