Different spark plugs are interchangeable. It is possible to interchange spark plugs with the same seat types. Spark plugs are only available in two seat types: flat and tapered. Spark plug cross-reference charts can aid in plug replacement. Angelfire.com and Progreengrass.com are websites that provide spark plug cross-reference charts.
A spark plug cross-reference chart contains different models of the plugs from various manufacturers and their interchangeable counterparts. For example, according to the chart, the NGK C7HSA spark plug is interchangeable with the AC S102F spark plug. The numbering system of the plug manufacturers helps to determine whether the plug is a substitute for another. Different spark plugs have different properties, such as heat range and gap dimension, that affect the choice of plug for a vehicle.