Procurement guide
Spark plug heat range
- Purpose
- Resolve spark plug heat range coding, thread/reach/seat notes and gap conventions before comparing substitutes across manufacturers.
Organize reference and vehicle details before comparing substitutes. Heat-range numbers are manufacturer-specific; similar digits across brands do not prove equivalent thermal behavior.
Fitment Guide decision points
Vehicle identity
Provide model year, make, model, engine code and relevant application notes. For a spark plug heat range inquiry, also record whether the buyer is matching an OE listing or evaluating a supplier-proposed substitute. Torque procedures and installation steps stay with the installing workshop; this service only collects the purchasing questions.
Reference cross-check
Use OE or supplier reference as an inquiry input, not proof of authorization. Ask the supplier to map the quoted heat-range designation to the same manufacturer’s application listing and to state the cross-reference source if another brand’s code was used. Keep coding conventions distinct rather than assuming similar numbers represent the same specification.
Interface check
Confirm thread diameter, reach, seat type, terminal style, gap with units and electrode construction. Request whether gap is factory-set for the quoted reference and whether boots or wires are included. New versus remanufactured condition must still be disclosed when used. Projection and seat sealing must match the application even when electrode material looks familiar.
Alternative review
Ask the supplier to explain differences before approving substitutions. A hotter or colder heat-range proposal is a deviation that needs written buyer approval. If a kit mixes electrode families or heat-range codes, keep each line visible so sample approval cannot silently cover the wrong plug.