Reading the Tea Leaves, er... Plugs.

I recently purchased a 2000 C2 coupe with 68K miles. I got very little service history with the car so I'm trying to replace as many of the common wear items as I can. Tonight I pulled the plugs, which despite all of the horror stories (or perhaps because of them) wasn't that bad. Plugs look like perhaps they were OE. They don't look particularly bad (except perhaps the center electrode of #2) but it almost seems like there was some copper anti-seize on some of the ground electrodes. It looks oily in the photos, but it's really more sticky like anti-seize and only on half of the electrodes of those plugs affected (lower electrodes when plug mounted in horizontal position?) I thought this odd as doesn't Porsche recommend not using anti-seize anyway? Or is there something else going on? I got Bosch 7413 replacement plugs from Pelican. The Bosch website claims "Nickel-plated rolled threads is used for complete anti-seize and corrosion protection" which must read better in German. Anyway, I was planning on installing the new ones without anti-seize. Thoughts/advice? [Click on the photo below for a bigger image.]

Never use anti-seize on a spark plug. Too easy to foul when installing. It also will affect the torque value that you are supposed to use.

Those plugs look excellent. Your engine is in good shape.

Plugs look good. If they are factory, they could have a light coating of a thread lube. The threads look very clean. Different manufacturers have their own rules (recommendations). Harley-Davidson always uses anti-seize on the TC and XL motors. I once pulled the plug on a customers bike and threads came out with the spark plug. This was a costly and easily preventable situation. I'd rather short or foul a plug than strip a threaded hole. I've used a light application of anti-seize for years, decades even on motorcycle plugs going into aluminum without ever a shorted plug as a result. I'll use anti-seize when I change the plugs on the Turbo too. Don't do what I do, go by the book. I'm obstinate by nature.

With the engine not exhibiting any issues the plugs were fine though probably due to be changed if not based on miles then time. Sure they came out ok for you but the car might have lead a sheltered life while another car driven year round in all weather might have suffered from plug thread corrosion after that much time. Unless it is called for in the factory manual you should not use anti-seize. From the plugs I have seen the threads come with a speiclal light powdery coating that is sufficient. When a thread lube is used this leaves a tiny porous gap between the threads of the plug and head. Combustion byproducts can accumulate and lead to corrosion, plug loosening or even leaking as the plug moves about some from the forces of combustion. When a plug hole that has had thread lube in it gets a new plug this new plug can scrape the old thread lube residue and push it ahead of and into the combustion chamber. It may not do any harm there but the material is very bad for O2 sensors and converters. Sincerely, Macster.

I've used anti-Seize on plug threads for years. Copper is for high heat..silver is for the more normal engines. You should see the guys who come to me with busted plugs and are looking for some way to extract the remains. Generally they don't or haven't used anti seize on the plug threads. These are on primarily engines with cast iron heads...the aluminum heads will sometimes and perhaps not often..take the threads out too..Then somebody is looking for a helicoil setup (gasp! horrors!)...not good to do...But if plugs are changed regularly this is not the case...All these 100K mile plug changes are just asking for trouble.(IMHO)....

Your plugs look very similar to some I just pulled out of an 8 year old, 25K mile Cayman engine. That is, your electrodes and insulator wear and coloration are similar. But the threads on your plugs are considerably cleaner and it makes me wonder all the more why mine were so "gunked up". I changed mine due to the time elapsed, not the mileage. Had no trouble removing them, but I could feel the brown gunk on the threads when I was unscrewing them from the heads. It was as if the factory had installed them lubed up with oil or something.

Change the sleeves and '0' rings as well as the plugs if the 2000 has them. My 99 had them. It's an easy job while you are in there. I didn't change the coils. My plugs looked cleanish like your do but I was amazed on the difference the new plugs and sleeves made to the performance of the engine. You will need a boat plug to remove the sleeves.

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Well, your limited experience is not nearly sufficient to overrule what Porsche says about using anti-seize. Anti-seize is clearly not called for in the case of Porsche spark plugs (and I can't recall it being required for other modern cars I have owned). The plugs leave the factory with no AZ. If they are replaced by factory trained techs the replacement plugs receive no AZ. AZ puts the O2 sensors at risk of damage from the AZ. Furthermore AZ puts a layer of material between the plug threads and the head threads. This interferes with the flow of heat from the plug to the head. It also provides a gap for combustion gases to get between the plug and head threads where it will lead to corrosion and possibly cause the thread damage you seek to avoid by using AZ in the first place. If you look at the picture of the plugs you can see the threads are discolored starting at the combustion chamber end of the plug. This is from combustion gases being forced between the (tiny) space between the plug and head threads. I note this space is as tiny/small as it can be with no AZ used. The only way to ensure the lowest chance of thread damage is to use the right plugs, which should have a proper thread finish to ensure a good seal and proper friction to obtain the proper tightening torque, to install them correctly, and to change them when due, either on miles or time. This brings the risk factor of trouble at the threads to as low as it can ever be and doesn't put any of the other components -- O2 sensors -- at risk of degradation due to AZ contamination.

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The factory doesn't install the plugs with any lube. (In fact there is a video posted here somewhere -- I've seen it on several forums -- that shows a Porsche engine being assembled and not only are the plugs installed with no lube -- which I expected -- none of the engine parts I saw installed were pre-lubed, which is amazing to me.) What you saw was the result of the plugs remaining in service beyond their time limit. Combustion gases get forced in between the threads of the plug and the head. This forms corrosive compounds which attack both the plug and head material. I believe 8 years is about double the time the plugs should have been replaced based on elapsed time. Had you delayed this service there might have been plug thread or head thread damage. This would have been blamed on the lack of thread lube not the fact the plugs were left in service probably double the time they should have been in service.

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I'm sure ethanol in the gas doesn't help. That's why I always avoid it.

Macster, Time based spark plug interval? So should the pistons be changed based on time to? Where do you get this info/theory from?

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Yes, I know the factory does not use anti seize or a lube. I was just wondering what the dark sticky gunk on the threads was. My understanding of the reason Porsche recommends plug replacement at four year intervals is due largely to avoid the plug seizing in the head. But as I noted above, at 8 years there was no sign of the plugs becoming seized and instead there was an oily sticky layer found on the plugs which rendered the plugs easy to break free and remove. I would think that ambient conditions (humidity, heat, cold, etc.) and mileage on the plugs would have far more to do with the plugs seizing than time elapsed. In any case, I will be changing my plugs based mostly on mileage but with some thought given to time as well. The point of my post was to describe what I saw on my plugs compared to the OP, and I was hoping others would comment about what they are seeing. Right bank-old plugs next to new plugs

If the plugs were not original, it is nearly impossible to know if something was used or not on the threads. If the plugs are original what you are seeing on the threads is what comes from the exposure to combustion gases over the miles. I have seen something similar from every set of plugs I have had removed from my Porsche engines over the years. And I know the plugs went in sans any thread lube. While you may have not encountered any difficulty removing the plugs even after so many years, others may not be so fortunate. I expect the change by time schedule is a bit conservative and many manage to let this go and avoid any problems. (My 03 Turbo when I bought it used in 2009 was overdue on plugs and I had them changed and they didn't look too bad. But the plugs had only covered 10K miles.) The plugs are the sacrificial component in the plug/head thread interface. The plug change schedule is what it is to avoid the chance of while getting more service life out of the plugs to ruin a head in the bargain. I can buy a lot of spark plugs for what it would cost me to replace one or both heads on even my 02 Boxster. I don't even want to think about what new heads for my Turbo's engine would cost.

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Where do you dig up this stuff? Who told you the plugs have a shelf life based on time? Long life spark plugs are nickle plated so they don't corrode into the head between the 100K mile change interval. The fact that they are cheap is no reason to uselessly change them all the time. Aluminium is soft (compared to cast iron) and reducing the unnecessary reasons to change the plugs will only be good for it.

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Guess everyone thinks the only wear that takes place is at the plug tip. Look at the plug threads. They are corroded. While one can't view the head threads aluminum also corrodes. Why you (editorial you) refuse to recognize corrosion as a force to be considered in servicing frequency is beyond me. If you subscribe to 100K mile plugs regardless of how long it takes to accumulate 100K miles then leave the plugs in until you reach 100K miles.

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You didn't answer my question.

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Thought it was clear. Porsche recommends changing plugs after so much time regardless of miles. I was only recommending owners follow Porsche's guidelines regarding changing plugs based on time.

Porsche plugs are much closer to the road,moisture,salt etc. than most.

Macster, I think Imo's question is a fair one. Where/how did you arrive at the statements that you are making? Don't take this as accusatory (at least not from me), but simply wondering what source this comes from. It makes sense that the brown gunk on the threads could be caused by combustion gases. However I don't think there was any real corrosion going on. When I cleaned the gunk off of one of the plugs the threads looked sharp and intact, so they were not corroded enough to be seen by the naked eye.

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And how is this relevant when they are completely sealed from the elements by the coil?

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You were doing a lot more then "I was only recommending".