[Grady Clay]

As you can see (and your further research will show) there is quite a diversity of opinion.

I tend to separate sparkplugs into two groups: cheap and expensive. I have had engines that I want to use new sparkplugs more often than oil changes. That can be for a variety of reasons; diagnostics (chasing MFI gremlins), selecting heat range, etc. for that day’s activity (mountain tour, PCA DE event) or to simply save my ‘expensive’ plugs. There is too much Scot in me to waste money.

‘Expensive’ sparkplugs have a definite use. There are clearly technical advantages in many circumstances. Features such as platinum (a catalyst), fine-wire (high potential field density) and others are clear benefit. Many times these features allow a given sparkplug to operate successfully over a wider set of operating conditions (typical for normal street use) and give an extended service life.

Anecdotal testimony may be useful for sorting out the ‘charlatan’ junk. Personal testing is very difficult because of the cost and small sample. Manufacturer’s choices may be influenced by factors that aren’t important to you (how much does Exxon pay Porsche for Mobile 1 to be OE?)

I suspect Bosch goes to considerable technical effort in conjunction with Porsche’s research fo find the best ‘recommended compromise’ for sparkplugs for our old engines. I think there is little in common with the current technology engines.

Probably the best we can do is to understand the published technology and settle on a high-end group of sparkplug types. I suspect only an exhaustive (and expensive) research study could do better.

You will find many cases where there are reports of “I installed XYZ and my 911 ran best ever.” Seldom do I see someone putting his ‘old style’ plugs (but new examples) back in and having the 911 revert to previous ‘poor running’.

There are also a myriad of other conditions that affect the seeming sparkplug performance. High on the list is the type and condition of the ignition system as a whole. Others include the age and condition of the engine, injection (carb) settings and condition, exhaust, fuel, environmental conditions, driving conditions and sometimes just the ‘phase of the moon’.

You should note that sparkplugs (along with tires, oil and filters) probably have the largest marketing costs associated with the price you pay.

Best,
Grady