Autolite 666 Spark Plug

Autolite 666 Copper Resistor Spark Plug

Autolite 666 is a copper resistor spark plug built for OE-style replacement in a wide range of classic GM, Ford, Jeep, and Cadillac applications. It delivers quick starts, smooth acceleration, and dependable ignition performance for vehicles that call for a 14 mm tapered-seat plug with a 0.060 in. pre-gap.

The Copper Resistor Spark Plug line from Autolite focuses on OE form, fit, and function at a value price. For drivers maintaining older Chevrolet S10, Buick Regal, Pontiac Firebird, or Jeep CJ models, this plug provides the core specifications needed for direct replacement service.

Key Features

• Copper core center electrode for consistent ignition response
• Resistor design with 4,000 ohms resistance
• Nickel center and ground electrode tip materials
• Tapered ground electrode tip design and tapered seat type
• Pre-gapped at 0.060 in. / 1.50 mm
• Ceramic insulator with mid-projection design
• 14 mm thread diameter, 5/8 in. hex size, and 0.433 in. reach

Detailed Description

Autolite 666 is engineered as an OE-style spark plug replacement for many domestic vehicles from the 1970s through the early 1990s. It is a direct service choice for applications such as 1985-1993 Chevrolet S10, 1980-1991 Buick Skylark, 1980-1986 Pontiac Firebird, and 1980-1983 Jeep CJ5. The copper center electrode supports reliable spark delivery, while the resistor construction helps control electrical noise in the ignition system.

This part cross-references DENSO Auto Parts 5021 and Valeo 17 for the same application. If you are searching for an Autolite 666 spark plug for Chevrolet S10, Buick Regal, or Pontiac Grand Prix service, this OE-style replacement matches the listed fitment and specifications.

What It Helps Solve

• Hard starting caused by worn or fouled spark plugs
• Rough idle and inconsistent combustion
• Loss of throttle response during acceleration
• Ignition noise concerns in resistor-equipped systems
• Maintenance replacement for aging OE-style plugs

Installation Notes and Tips

Verify the vehicle’s required gap, seat style, thread diameter, and reach before installation. This plug is pre-gapped at 0.060 in. / 1.50 mm, but older applications listed in the fitment data may call for different gap specifications depending on engine calibration and model year. Use the correct 5/8 in. spark plug socket and confirm the terminal type matches the ignition lead or coil connection.

Compatible With: Fits 1985-1993 Chevrolet S10, N/A; Fits 1991-1993 GMC Sonoma, N/A; Fits 1980-1992 Buick Century, N/A; Fits 1990-1992 Chevrolet Lumina, N/A; Fits 1982-1992 Oldsmobile Cutlass Ciera, N/A; Fits 1987-1992 Oldsmobile Cutlass Cruiser, N/A; Fits 1980-1991 Buick Skylark, N/A; Fits 1988-1991 Oldsmobile Cutlass Calais, N/A; Fits 1982-1991 Pontiac 6000, N/A; Fits 1985-1991 Pontiac Grand Am, N/A; Fits 1985-1990 Chevrolet Astro, N/A; Fits 1982-1990 Chevrolet Celebrity, N/A; Fits 1985-1990 GMC S15, N/A; Fits 1985-1990 GMC Safari, N/A; Fits 1985-1988 Chevrolet S10 Blazer, N/A; Fits 1985-1988 GMC S15 Jimmy, N/A; Fits 1984-1988 Pontiac Fiero, N/A; Fits 1982-1987 Buick Regal, N/A; Fits 1985-1987 Chevrolet Monte Carlo, N/A; Fits 1984-1987 Oldsmobile Cutlass Supreme, N/A; Fits 1984-1987 Pontiac Grand Prix, N/A; Fits 1982-1986 Chevrolet Camaro, N/A; Fits 1984-1986 Pontiac Bonneville, N/A; Fits 1980-1986 Pontiac Firebird, N/A; Fits 1981-1982 Cadillac DeVille, N/A; Fits 1981-1982 Cadillac Eldorado, N/A; Fits 1981-1982 Cadillac Fleetwood, N/A; Fits 1981-1982 Cadillac Seville, N/A; Fits 1980-1983 Jeep CJ5, N/A; Fits 1983 Jeep CJ7, N/A; Fits 1983 Jeep Scrambler, N/A.

Quality Assurance

Autolite supplies ignition products to the automotive aftermarket and original equipment manufacturers, with a product line built around OE-style replacement requirements and broad vehicle coverage.