To reduce the costs of vehicle ownership and maintenance, many car makers say the oil filter only needs to be replaced at every other oil change.

The oil filters on most engines today have been downsized to save weight, cost and space. The "standard" quart-sized filter that was once common on most engines has been replaced by a pint-sized (or smaller) filter. You don't have to be a rocket scientist to figure out that a smaller filter has less total filtering capacity. Even so, the little filters should be adequate for a 5,000 km oil change intervals -- but may run out of capacity long before a second oil change.

Replacing the oil filter every time the oil is changed, therefore, is highly recommended.

An engine's main line of defense against abrasion and the premature wear it causes is the oil filter. The filter's job is to remove solid contaminants such as dirt, carbon and metal particles from the oil before they can damage bearing, journal and cylinder wall surfaces in the engine. The more dirt and other contaminants the filter can trap and hold, the better.