At what mileage is it recommended to swap them out?

 

I bought a 2006 last year with 27k miles on it. When it hit 30k I bought it a full "tune-up" including plugs because I had no car history. I felt 10 years was enough time regardless of miles.
I think they are supposed to last up to 100k miles.

 

our '08 c4 had 27 K on it when we bought it and I changed the plugs and coil packs at 35K. noticed no difference in performance...just peace of mind. Buddy and I did it for less than $500.00 which included cabin and engine air filter. Took about 5 hours but could do it in half that time now. Dealer wanted around $1500.00 just to do plugs and filters. We felt that we might as well do coils since you have to pull them anyway.

 

coils has hairline cracks at 36K miles (no code) so the 8 yrs old plugs were also replaced. Noticed good throttle response.

 

I replaced mine after 10 yrs, 33k miles and they looked great with no abnormal wear on the electrodes. Main reason for replacing mine was due to misfires, which were caused by a bunch of hairline cracks on the coil packs. The plug replacement was mainly "while I was in there". Dealer mechanic said plugs can go 60k regardless of age- within reason (not 15-20yrs). But 10 yrs apparently is ok based on how mine looked.

 

Exactly!

@OP depend condition and age of coil pack, have them replaced along with spark plugs...labor is cheaper in long run.

 

I think, if you do regular Services at a Porsche Dealership, they will replace them after 4 years or about 60k (whatever occurs first), if I recall right.


At least mine were replaced twice in 2009 (22k) and 2013 (32k) on my 2005 997.1 while a serivce was performed

 

The issue with plugs - and the reason to replace them - I think every 5 (or 6) years or 40k miles - is that they can get bonded to the engine.

 

I attended a PCA sponsored tech meeting at a local Porsche dealer recently. I did ask one of the service techs about spark plugs being left in cars longer ( time wise) than the service schedule indicates. He responded by saying that they have never had a problem removing spark plugs from cars that had plugs left in over extended periods of time ( e.g. 10 years and 30 K miles)

 

I change urs and coil packs about every 30,000-40,000 miles. I wonder if the redesigned coil packs with the thicker back (requires longer bolts) will last longer before developing cracks and causing misfires.

 

The failure mode of the plastic housings used for coil pack is hydrolysis. This is the result of a material susceptible to this degradation mode and exposed to elevated temperatures and water/moisture. The material chosen for that fits that scenario. It maintains its physical and electrical properties at elevated temperature but will eventually be degraded by heat/moisture combination. So, yes, it will ultimately fail as well if exposed to the same environment.

 

The miles at which plugs need to be replaced varies. Best to touch base with the dealer and get the latest on this. Sometimes Porsche reduces the miles, other times it increases the miles.

There is a time call out too. While I use my cars often enough the plugs always get changed triggered by mileage not time but if not I'd also adhere to the change by time schedule and I'd recommend you adhere to the change by time schedule, too.

If you look at a used plug you'll see the plug threads are discolored from combustion gases being forced between the plug and head threads. The discoloration starts at the tip and goes upwards.

Now even if the plug/aluminum head threads do not corrode to the point the head threads suffer degradation, the discoloration shows the combustion gases are getting forced between the threads.

This works to degrade the heat transfer from the plug threads to the head threads and into the head proper (where coolant removes the heat) and the plug then runs hotter than it normally would.

This can result in performance degradation possibly even damage to the plug. You do not want a plug coming apart from excessive heat (or any reason really) in an engine.

 

It varies by model year per the Porsche maintenance checklists:


2005-2007 - 60K miles or 4 yrs
2008 - 36K miles or 4 yrs
2009 onwards - 40K miles or 4 yrs


Not sure what happened in 2008???

 

While we're on the topic, I noticed when I was cleaning my wheel arches that my coils say "Beru" on them; I assume those are aftermarket replacements unless Beru is the OEM supplier? I bought mine a little over a year ago with 40k miles so I think they've been done but I don't know for certain.

 

Beru is OE.