Spark plugs don’t require replacement very often, they can go years and many miles before replacement is a must. However, most manufacturers would suggest having a replacement installed every 40,000km while type and condition of the spark plug is a key factor e.g. copper plugs which have the shortest life span compared with plugs made from more durable materials. Some key characteristics that indicate a spark plug change are; difficulty with starting your vehicle, rattling noises or knocking from the engine bay and inferior overall performance. Mis-firing spark plugs can also have an adverse effect on fuel economy too, that’s why we recommend having your plugs inspected at minimum 20,000km.
For more information on how spark plugs work.