Quick guide to spark plugs
DriverSense - Kevin Fleming
Seemingly simple for many decades, spark plugs are now more complex than ever before.
Whenever it comes time to change my spark plugs, I always find myself questionably browsing the selection at the local auto parts store. There always seems to be more choices of spark plugs for my particular auto than there are generic upholstery cleaners. Some cost two dollars, while other cost twelve dollars or more. Then there is the question of what the plugs themselves are made of. Should I go with copper, platinum or iridium? Let’s see if I can make sense of this jumble of spark plugs for the adventurous do-it-yourselfer.
How The Spark Plug Works
Before we get into the specifics of the variety of spark plugs out there, it will help to clarify how exactly a spark plug works. A spark plug fits neatly between the piston and valves of an engine in order to provide the “spark” needed for combustion. Of course, this only occurs in a gasoline engine, as a diesel engine combusts fuel by heat alone. In the case of a gasoline engine, air and fuel enter the combustion chamber and the spark plug sparks, adding the final element to the equation.
A spark plug manages to do this by drawing an electric current from the engine itself. It does so by either a distributor on an older engine or a coil pack (coil on plug) on a newer engine. If you have ever taken a look under the hood of your auto, you have probably seen the wires that connect from one of the two previously mentioned devices to the spark plug terminal itself. To make a long story short, the electric current is transferred through the plug to the side and centre electrodes, which sit in the cylinder chamber itself.
The electrode of a spark plug is the part of the plug that is coated with copper, platinum or iridium. When a spark plug goes bad, it is usually because one of these elements has essentially vaporized off and is unable to conduct electricity efficiently. In some cases, a plug can go bad because it is 'fouled' up with carbon or oil. Other times, spark plugs electrodes can become burnt out from too much heat in a high performance engine.
Now The Choice
The first rule of thumb is always to follow your auto’s owner’s manual. It should detail the exact size of the plug you need, as well as the correct gapping and variety of plug needed. Typically, this information can be found in the service or maintenance section of the manual.
However, if you have done a little work to your auto’s engine or are simply curious, the variety of plugs out there can be daunting to select from. Most standard performance autos usually require a plug that is made of copper. Copper has essentially been the standard of spark plugs for decades, but as we will see, it is slowly becoming a figure of the past. It isn’t that copper is a bad conductor of electricity or is less efficient than the other kinds of plugs, but rather, a copper plug typically only lasts 30,000 to 45,000 miles. In other words, you are more than likely going to have to replace your plugs a few times while you have your auto.
The figurative replacement of sorts for copper plugs is platinum. The advantage of platinum over copper is that platinum lasts much longer. Compared to 30,000 to 45,000 miles in a copper plug, a platinum plug can last for 80,000 to 100,000 miles. Most auto manufacturers include these plugs from the factory these days in order to allow for a convenient 100,000 mile tune-up. However, the one downside to a platinum plug is that platinum is quite expensive in comparison to copper and platinum.
Finally, we have iridium plugs. Iridium plugs are the new craze because they last just as long as or even longer than platinum. Because iridium lasts longer than platinum, it means more consistent performance throughout the life of the plug (i.e. iridium is roughly six times harder than platinum, hence it does not vaporize as fast). Plus, iridium is far less expensive than platinum.
More From DriverSense:
