Don't ignore spark plug replacement

By Doug McAllister

Last week I wrote about vehicle owners pushing oil-change intervals out too far. I alluded to other services that are not required, according to the manufacturer, until 100,000 miles.

One of those services I was referring to is spark plug replacement. Many cars today have iridium spark plugs that really can last a long time compared to a standard spark plug.

However, spark plug threads are made out of metal compound. Most of the cylinder heads they thread into today are aluminum. Often we run into a situation where the spark plugs have been in the vehicle so long they won't screw out of the cylinders. Or when they do come out, the threads are damaged.

Another problem with leaving spark plugs in this long is the fact that, as they wear, the gap over which the spark jumps becomes wider over time. As the gap becomes wider, the spark has to jump further, which creates heat downstream. This heat can have an adverse effect on ignition coils and or modules.

Finally, the ceramic part of the plug can come loose from the metal, allowing engine compression to bypass through the plug, damaging the boot and ignition coil.

Talk to your service provider about when the right time is for you to change your spark plugs. Changing them earlier than the recommended interval may save you money in the long run.

• Douglas Automotive is at 417 W. Main St., Barrington; 123 Virginia Road, Crystal Lake; and 416 Northwest Hwy., Fox River Grove. For information, visit douglasautomotive.com. Send questions to underthehood@dailyherald.com.