Tuesday, April 7, 2009

Are platinum spark plugs better?

Are platinum tip spark plugs better? In a word..... yes.

In eight words..... Yes, if the vehicle is designed for them.

Here we have some platinum tip spark plugs that were removed from a vehicle this weekend. The Chrysler product they lived in had 140,000+ miles on the clock, and these are the original spark plugs.

Yes, that is excessive in the extreme, but it's a testament to their design that these plugs lasted that long, and the vehicle ran well right up till a few days ago.

What makes these plugs last so long are two main points. Modern computer controlled vehicles run so cleanly, and burn the proper fuel mixture with the proper spark timing, that plugs just don't foul like they used to. In addition, the platinum tip on the spark plug is resistant to wear, as the electrons flow in massive numbers from one electrode to the other.

The actual platinum part is only a minuscule disc on one electrode (or both in double platinum plugs). It's the final tip of the electrode and the spot where ionization of the gap begins. As long as it remains on the plug, it will stay mostly unworn and be able to create the high voltage arc effectively. Once it wears away or breaks off, the plug begins to wear like a normal spark plug, only more rapidly.

The reason I say "If the vehicle was designed for them" is simple. Platinum spark plugs require higher voltage to work well, and an ignition system with not only higher output but more coil reserve and saturation time at higher RPM. Coil-over-plug systems are a natural for platinum tip plugs, and most new cars come equipped with them. The problems begin when someone falls for the advertising and installs $8 a piece double platinum plugs into a vehicle designed for $2 standard spark plugs. Now the rest of the system is being challenged, and typically is not up to the job. As a result, mileage and performance fall while ignition system components fail in droves trying to meet the demand.

When replacing spark plugs on vehicles with high mileage, give strong consideration to also replacing the ignition cables (spark plug wires) as well. They are often damaged through age and harsh use, but seldom show it except to the trained eye.

The two plug wire boots dissected in the image below show it better... the one on the left has heavy carbon trails from the truly excessive voltage demand. The one on the right appears normal and is still usable. From the outside, without cutting them apart, only a strong light and a sharp eye would have noticed the issue.

That, my friends, is the end of the lesson for today. Please deposit a quarter in the instructors pay box on the way out the door.

Have a nice day!


mIsho said...

How does one know if their car can handle the platinum jobs?

Carteach0 said...

If the factory recomended spark plug is platinum, then you are good to go. If not.... probably best to stick with what the system is designed for.