Answer: If regular maintenance and inspection isn’t performed on your engine, your vehicle may not be operating as reliably or efficiently as it should. A well-tuned engine operates at maximum performance levels. During a tune-up, engine parts that affect performance are checked and replaced. Spark plugs create an electrical spark that ignites the gasoline/air mixture in your engine. They create, and must be able to withstand, a tremendous amount of voltage and heat. If your engine’s spark plugs aren’t working properly, your engine can stall and may not even start. Spark plug wires are also very important. They have to be able to transfer and withstand the voltage created by the spark plug. If they are old, they can burn out and cause a misfire. Fuel and air filters are two more items that are checked during an engine tune-up. These two items affect engine performance and gas mileage. Fuel filters help protect your engine’s fuel system. They trap dirt and other debris in your fuel and don’t allow them to reach your engine. Over time, a fuel filter will clog and won’t allow fuel to flow freely. This can lead to poor acceleration and poor engine performance. Engines also require a free flow of clean air to operate. Outside air travels through the air filter and mixes with your vehicle’s fuel to power your engine. Air filters trap the dirt and other debris from the outside air. As with fuel filters, air filters can clog over time. A dirty air filter can cause your vehicle to lose up to 20 horsepower, while making your engine work harder, since it restricts airflow. A dirty air filter will also reduce your gas mileage. Your engine requires the exact amount of air and fuel, but with decreased airflow there is less air mixing with your vehicle’s fuel; therefore, your engine uses more fuel to compensate.