Spark plugs are replaced every 80,000 miles. Many vehicle manufactures claim their spark plugs can last up to 100,000 miles, but as the gap in the plugs widen, the chance of vehicle problems rises significantly. Some of these problems include bad gas mileage and reduced engine performance.
Have spark plugs inspected every 30,000 miles or at the same time that air filters and brakes are inspected. During replacement, the new spark plugs must be the same specification as the original factory plugs. If spark plug wires are on the vehicle, they need to be inspected thoroughly at the same time the plugs are replaced.