The 100,000+ Mile Spark Plug

Some car manufactures are recommending 100,000 miles or more between spark plug replacements.

Under ideal conditions (which usually means no town driving, no stop and go driving, no high speed driving and temperatures between  30 and 75 degrees F) a set of Platinum/Iridium spark plugs can easily make it to 100,000 miles with no problems.

Most of us do city or stop and go driving, short trips or driving in hot weather which causes more rapid wear on the spark plugs.

As the spark plug electrodes wear, voltage demands to create a spark keep increasing, leading to burned-out modules, coils, spark plug wires and other ignition components. Poor spark plug performance can also cause poor engine performance, mileage loss and hard starts. We see quite a few cars drive or towed in with these problems between 80,000 and 100,000 miles.

Today’s computers are able to hide many problems that would cause an older car to have a serious performance problem, but if those problems aren’t detected before they multiply or get worse a highway breakdown may be imminent.

We recommend spark plug replacement at 30,000 miles with normal spark plugs,  50,000 to 60,000 miles on normal Platinum plugs and 70,000 to 90,000 on Iridium or "100,000 mile" plugs. Performance and mileage degradation usually starts shortly after these recommendations on spark plugs with average driving.

Often forgotten are the fuel and air filters which still have to filter the same dirt out of the gasoline and air to prevent expensive repairs to the fuel injection system and engine.

Spark Plugs can seize in the engine due to metal transfer from dissimilar metals, heat and carbon. The best preventative measure is using anti-seize on the spark plugs, especially on aluminum cylinder heads. Unfortunately this will not help much if hard carbon deposits form on the spark plug in the cylinder. This may destroy the threads as the spark plug is removed, requiring repair. 

If you encounter a spark plug that will not come out, first soak it with a good penetrating fluid for about 12 hours. If the spark plug turns out a little and then seizes don't try forcing it out any further. Spray the exposed threads with penetrate and turn the plug back in a little and then back out to where it stops. Continue this process of a little in and a little out, hopefully you will gain a little each time you turn it out until the plug comes lose.
This procedure takes time but may save the threads in the cylinder head or breaking the spark plug off in the engine.

Some Ford pickup V8 engines have a problem with the lower part of the spark plug breaking off in the head when removed because of carbon. On these, always soak the plug with a good carbon buster overnight after backing off about 1/4 turn. Any further and the plug may break.
If this does happen there is a tool for removing the broken piece without removing the head.

 

 

 

Wayne's Garage
27 E 27th Eugene, Oregon 97405	333 Q St. Springfield, Oregon 97477

 

Our staff has over 200 years of  experience to serve your automobile needs and with our dedication to Integrity, Quality and Exceptional Service, Wayne's Garage can service or repair your car or truck to give you dependable transportation and "peace of mind". Our office staff will explain the needs or problems with your car in a language you can understand. We use original equipment parts whenever possible and offer an 18 month warranty. 
Visit us in Eugene or Springfield Oregon.