Opinions concerning spark plugs
 

Reference routine maintenance:

My 1999 Boxster is my daily driver and I focus on properly maintaining it. I now have well over 228,000 miles. I change my oil & filter every 10,000 miles and I change my sparkplugs every 30,000 miles (During the last two sparkplug changes I've used Bosch Platinum +4 plugs).

My question is this: Do I really need to change sparkplugs every 30,000 miles?

I am interested in your opinions on sparkplugs. I know early model 986s have different maintenance intervals than later model 986s.

I purchased it 5 years ago last September with 104,000 miles. In the past five years I have replaced the water pump twice and the AOS about three times (it failed again two weeks ago). I don't abuse it and I seldom rev it past 4500 rpm.

Thanks
MNC-I

Several years ago, when TRG was still racing Porsche, the region I was in had a tech session there and we had an opportunity to ask questions of the Porsche engineers who were there. The question of the four tipped plugs came up and both engineers didn't recommend them because they found they burned no better than a twin tipped plug and they cited instances where four tips increased the chance of a tip breaking off and damaging the motor.
I also bought my '99 used and it had 74K miles on it and there was no record of the 60K service being done so I went ahead and did it. 30K miles later I replaced the plugs in accordance with the service manual and could barely tell the difference between the new and used plugs. I suspect there is more to the service than that though and think changing plugs at 30K intervals gives the mechanic a chance to inspect the liners for cracks and oil leaks as well as the coils and coil wires.
I feel your pain on the water pump as I've had three in mine in 40K miles. They appear to have too small a bearing for the job they have to do. Why Porsche designed in the heart of the WC system with too small a bearing is as baffling as the IMS which is a bearing designed for air cooled use.

I've used the Denso iridium plugs and was not happy with them. After 20k I had to replace one do to the tip being burned so bad I got a misfire CEL. At 30k, I changed them all for Bosch, and two more of the tips were going.
Bosch have always looked good when I changed them, and I wondered if they could have gone a lot longer.
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