Bosch FR78 Super 4 Spark Plug

The Bosch FR78 Super 4 spark plug features a four ground electrode design that improves ignition reliability and combustion stability. It is engineered with enhanced electrodes and a surface air gap design to reduce carbon deposits and improve fuel burn efficiency. Typical factory gap is around 0.9 mm, and it uses a flat mouldable sealing seat with resistor suppression for stable performance.

Best for: Everyday passenger vehicles needing improved combustion and reduced fouling over standard plugs.

Bosch Super 4 FR78X Spark Plug

The Bosch FR78X is similar to FR78 but comes with a slightly larger factory gap (about 1.1 mm). Its four ground electrodes and surface air gap design help promote consistent ignition across different driving conditions and help protect the combustion chamber from carbon buildup.

Best for: Applications where a larger spark gap is required — often matched to specific engine tuning or OEM specs.

Bosch Super 4 WR78 Spark Plug

The Bosch WR78 Super 4 spark plug retains the four electrode layout to enhance spark stability and combustion. It typically has a 0.9 mm factory gap and a slightly larger hex size for different tool fitment. Its surface air gap electrode arrangement assists in resisting carbon fouling and delivering reliable ignition.

Best for: Engines where an enlarged hex size and specific gap are preferred for installation or OEM design.

Bosch Super 4 FR78NX Spark Plug

The Bosch FR78NX Super 4 spark plug is an extended reach variant designed to fit deeper recessed combustion chambers. It includes four ground electrodes with a 1.1 mm factory gap, surface air gap design to help maintain spark integrity, and resistor suppression. Perfect for certain larger engines and specific applications requiring deeper spark plug reach.

Best for: Vehicles with engines needing longer reach spark plugs, such as larger petrol engines.

Bosch Super 4 Spark Plugs (various) – HR78NX

The Bosch HR78NX Super 4 spark plug also uses four ground electrodes and the surface air gap design for improved combustion and fouling protection. It differs from the others mainly in its conical sealing seat and moderate thread length, allowing it to seal in engines that require that seat type. It keeps the typical Super 4 benefits of stable combustion and longer life.

Best for: Engines that specify a conical spark plug seat and benefit from four electrode ignition.

What “Super 4” Means:

Bosch’s Super 4 series features spark plugs with four ground electrodes instead of the more common one or two. This design provides multiple possible paths for the spark, which can help maintain a consistent flame front, reduce carbon fouling, and enhance combustion stability and fuel efficiency compared with standard plugs.