Tryfon

Werid, I’m at 20-24 mpg. Pretty sure these are factory plugs and coil packs at 108,552 miles.

I have the AFE dry filters but that’s it engine wise.

marinerbc

Mine came to 17/19 mpg , it is 16 CTT with these Denso plugs and cosmo racing plugs
i always drive hard when possible .

yesterday was driving around town with very little highway here is the PCC trip screen

F SANE IL

Looks like you should fill up soon.

I'm going to try and get the Bosch plugs soon and see if there is a difference. The only thing I'd like to do before all this is drop by the dealer where the car used to go and pull up full detailed repair and maintenance history so I have a base point understanding of what was already done and what wasn't. Maybe the plugs and coils were done just before I got the car and don't even need changing.

deilenberger

Don't bother with the coils. The one you show in the photo above is the newest revision. I installed 8 of them today (well, my mechanic friend did..) after during a plug change we found 7 cracked coils. No misfiring - they hadn't started absorbing moisture yet and swelling up (my mechanic has taken them apart to see what fails - the crack lets moisture into the coil core laminations, which happily rust and start pushing on the windings eventually causing them to fail.. which is why swollen ones are the ones that failed..)

Anyway - my old ones were 948.602.104.11 - the new ones right from the dealer 948.602.104.14 - and I know they're the newest - the dealership just moved into their new building and restocked the entire parts department about 3 months ago. Anyway - if you don't have cracks - yours are probably fine. Hook up your diagnostics - any misfires will be shown. Mine have been at 0 for ages.

F SANE IL

Thank you don for this info. In this case, I think I'm going to order 4 stock, same part # coils to keep handy in case something decides to crack on a trip. I'm going to have a parts store in the trunk.

twodollardoug

So we are checking for "coil misfires '? Will it pinpoint which cylinders?

deilenberger

Sure will. 0 is a good number.

twodollardoug

It's a good "round" number.

twodollardoug

can you post a picture of a cracked coil? Is it something that can be seen from the top? Or is removal necessary?

deilenberger

There are lots of pics on the forum of them.. a bit of poking around will turn them up. The crack can't be seen without coil removal. They crack on the plastic covering the body/shaft of the coil - not in the head region. It's an in-line crack, from top to usually about where the step in the shaft is. In the case of some coils - if the coil is cool when you remove it - the crack may be very difficult to spot. I believe the crack opens up as the core of the coil heats up.. Once one cracks - the other ones probably aren't far behind it, so best bet is to bite the bullet and just replace them since the labor to check them/vs/replace is the same. At least my dealer has them in stock and Worldpac (large foreign car parts distributor lots of shops use) can get them in 1 day - they get them from Porsche (and price them at Porsche retail price..) If you aren't in a rush - they can be found considerably cheaper at some on-line Porsche dealers (like $42 on-line vs $60 retail local..) And you might as well get some hexoglobular screws too.. just for the ones that go missing down into the depths of the engine compartment.

twodollardoug

Ok. Thank you for the explanation. I checked my car and it showed zero misfits. I will include the "check misfire" in my maintenance schedule.

deilenberger

Mine also showed no misfits - and no misfires.. Still had 7 out of 8 coils were cracked. They just hadn't gotten bad enough to start misfiring (or - appear unfit for duty.. )

ElSpoon958

I'm always wary to at least check that the gap is the same on all plus before installation. And also, never use any lubricant or anti seize?! Are you mad, good sir?! Lol dielectric boot grease for the plug-to-coil connection and a little anti-seize around the plug threads never hurt anything. Have you ever stripped the threads on the head or had a stuck plug/coil boot? NO FUN! lol

RhinoComp

Most modern spark plugs like NGK or Bosch manufactured ones have nickel coated threads or similar and won't seize in the heads due to that, so the addition of anti-seize will actually throw off your torque spec potentially by 20-25%. Which means they're getting tightened further into the heads than they're intended and actually will increase the likelihood of the threads or even the body of the plug being damaged. NGK actually expressly states to never use anti-seize on the coated threads.

The dielectric grease certainly never hurts though!