Autolite 25 Spark Plug

Autolite 25 Copper Resistor Spark Plug

Autolite 25 is a copper resistor spark plug built for OE-style fit, smooth ignition performance, and dependable starting. It is a practical replacement choice for a wide range of domestic vehicles, including Chevrolet P30, Ford F-150, and GMC Safari applications.

Key Features

• Copper center electrode core for consistent ignition response
• Nickel center and ground electrode tip materials
• 4,000 ohm resistor design for reduced electrical noise
• 0.044 in. / 1.10 mm pre-gap size
• 14 mm thread diameter with 5/8 in. hex size
• Tapered seat and mid-projection ceramic insulator
• OE-style form, fit, and function for many domestic applications

Product Details

The Autolite Copper Resistor Spark Plug line is designed around OE replacement requirements, giving you a straightforward ignition service part for older and mid-1990s vehicles. Part number 25 uses a standard copper core for reliable spark delivery, a resistor element to help control interference, and a tapered ground electrode tip design for stable combustion performance. This part cross-references Champion Spark Plug 18 for the same application.

Compatible With applications such as 1987-1998 Chevrolet P30, 1980-1998 GMC P3500, 1996-1998 GMC Safari, 1996-1998 GMC Sonoma, and 1996-1997 Ford F-350. Additional fitment coverage includes many Chevrolet C/K trucks, Ford Bronco and F-Series models, GMC Jimmy and Yukon, and Pontiac Firebird and Grand Prix applications across the listed years. Part number 25 is also referenced in OE-style service searches for classic and late-model domestic ignition maintenance.

Common Uses

• Hard starting caused by worn or fouled spark plugs
• Rough idle from weak or inconsistent spark output
• Misfire complaints during routine ignition service
• Reduced throttle response from aged plugs
• Radio-frequency interference in resistor-equipped ignition systems

Installation Notes

Verify the vehicle-specific gap before installation, since some listed applications require a different setting than the factory pre-gap. Check thread reach, seat type, and terminal style against the original plug before service. For best results, install on a cool engine and torque to the manufacturer specification for the vehicle.

Quality Assurance

Autolite supplies ignition products to the automotive aftermarket and OE channels, and this spark plug is built to OE form, fit, and function standards for the listed applications.