A Guide to Choosing Spark Plugs for the 1987 BMW L6
Keep your classic M30 engine running smoothly with the correct spark plugs for reliable performance.
- For the 1987 L6's M30 engine, stick with traditional copper-core spark plugs from brands like NGK or Bosch for the best results.
- Avoid using platinum or iridium plugs, as they may not perform well with the vehicle's original ignition system.
- Always check and adjust the spark plug gap to between 0.028 and 0.032 inches before installation.
- Replacing the spark plugs is a simple, low-cost DIY maintenance job that can significantly improve engine performance.
Symptoms of Failing Spark Plugs
Worn-out spark plugs can cause noticeable problems with your L6's performance. As the electrodes wear down, the spark becomes weaker and less consistent. You might experience one or more of these symptoms:
- Rough Idle: The engine may shake or vibrate more than usual when stopped.
- Engine Misfires: You might feel a hesitation or stumble from the engine, especially during acceleration.
- Poor Acceleration: The car may feel sluggish or less responsive when you press the gas pedal.
- Reduced Fuel Economy: Inefficient combustion means you'll be visiting the gas station more often.
- Difficulty Starting: A weak spark can make it harder for the engine to fire up.
Choosing the Right Aftermarket Spark Plug
For many modern cars, expensive platinum or iridium spark plugs are an upgrade. However, the ignition system in the 1987 BMW L6's M30 engine was designed for traditional copper-core spark plugs. Enthusiasts and experienced mechanics agree that these classic-style plugs provide the best performance and reliability in these engines. The stock ignition system may not run hot enough to keep pricier platinum or iridium plugs clean, which can lead to deposits and poor performance over time.
Brand Recommendations
Based on owner experiences and OEM history, some brands are a better fit than others for your L6.
- Tier 1: Bosch & NGK
Bosch was an Original Equipment Manufacturer (OEM) for BMW, making their copper plugs a reliable, factory-spec choice. NGK is overwhelmingly recommended in owner forums as a top-quality alternative that performs flawlessly in the M30 engine. You cannot go wrong with a standard copper plug from either of these brands. - Tier 2: Denso
Denso is a well-respected Japanese brand known for high-quality manufacturing. While not as commonly discussed for the M30 engine as Bosch or NGK, their standard copper plugs are a solid and dependable option. - Tier 3: Champion
Champion is a widely available brand, but it is not frequently recommended by BMW specialists or owners for this specific application. While they may function, most owners prefer the proven track record of Bosch or NGK for their classic BMWs.
Pro Tip: Check the Gap!
The spark plug gap is the small space between the center and ground electrodes. For the M30 engine, this gap should be set between 0.028 and 0.032 inches. New spark plugs are not always pre-gapped correctly for your specific vehicle. Always use a feeler gauge to check and adjust the gap before installation to ensure a strong, efficient spark.
Cost of New Aftermarket Spark Plugs
The cost for a set of six new spark plugs for your 1987 L6 is very reasonable. Expect to pay for the parts and, if you choose, for a mechanic's labor to install them.
| Part Type | Price Range (Set of 6) |
|---|---|
| New Aftermarket (Copper) | $15 - $45 |
| New OEM (Bosch/NGK) | $25 - $50 |
| Shop Labor | $75 - $150 |
Frequently Asked Questions
Can I use platinum or iridium spark plugs in my 1987 L6?
It is strongly recommended to stick with standard copper-core spark plugs. The M30 engine's ignition system was not designed for platinum or iridium plugs, and using them can sometimes lead to fouling and performance issues because the system doesn't generate enough heat to burn off deposits.
How often should I replace the spark plugs?
For a standard copper plug in the M30 engine, a good replacement interval is every 25,000 to 30,000 miles or every 3-4 years to maintain peak performance. This ensures a consistent, strong spark and helps prevent other ignition system problems.
Is replacing spark plugs a DIY job?
Yes, this is a great DIY task for beginners. The spark plugs on the inline-six M30 engine are easily accessible on the top of the engine. The job requires only basic hand tools and can typically be completed in under an hour.
What is the correct spark plug gap for a 1987 BMW L6?
The recommended spark plug gap is between 0.028 and 0.032 inches. It is crucial to verify this measurement with a gap tool and adjust each new plug before you install it.
Technical Specifications
OEM Part Numbers: 12129061869 12121279599
Recommended Spark Plug Type: Copper Core Recommended Brands: NGK, Bosch Recommended Spark Plug Gap: 0.028" - 0.032" (0.7mm - 0.8mm) Engine Code: M30B34 / M30B35 Quantity Required: 6
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The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
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