For most cars and SUVs, the spark plugs need replacement every 30,000 miles (or at the interval of every 30 months). To find out the best recommendation, you should either check your car’s manual or visit the website of the vehicle manufacturer. If the spark plugs don’t function with maximum efficiency, you will face a wide range of issues with the engine of your car. How long spark plugs will perform depends on the type of spark plugs used in your vehicle.