Spark Plug Swap: OEM NGK [06K905601D] to NGK PLFER7A8EG [94833]

Back when I had my Stage 2 MK4 1.8T, I used to change out copper electrode plugs every 10-12K due to cheap, effective maintenance.
I was going to tackle the same on my used MK7 GTI, but due to the different "cup-shaped" terminal type on the spark plug, there wasn't an option to be found.
Wanting to have a baseline for future modifications, I went ahead and swapped out the OEM plugs and saw a lot of variance.

First, some background:
CAR: 2015 Volkswagen Golf GTI (MK7) w/ Performance Pack (purchased with 29,xxx miles)
MODIFICATIONS: none - stock power level
MILEAGE: 32,8xx miles (at time of plug swap)

Some history on the OEM plugs (P/N #06K-905-601-D), which were standard on 9+ different VAG vehicles of the current and previous generation:
* laser welded, dual platinum plug [both center electrode / ground electrode] w/ copper core
* NGK heat range = 7
* specified gap from NGK = 0.031" (0.8mm) - 0.035" (0.9mm)
* specified gap from Volkswagen = 0.032" [unconfirmed]

When I removed the OEM plugs, I measured the gap:
- Cylinder #1 = 0.034"
- Cylinder #2 = 0.032"
- Cylinder #3 = 0.035"
- Cylinder #4 = 0.035"

Visual Inspection - Cylinder #1:
- light gray ash on ground electrode = good air / fuel ratio
- slight peppering of side electrode = first indicator of overheating plug
- slight discoloration of side electrode = second indicator of overhearing plug
- HEAVY pinking of ceramic insulator = indicator of auto-ignition / knocking


Visual Inspection - Cylinder #2:
- light gray ash on ground electrode = good air / fuel ratio
- moderate pinking of ceramic insulator = indicator of auto-ignition / knocking


Visual Inspection - Cylinder #3:
- light gray ash on ground electrode = good air / fuel ratio
- moderator peppering on side electrode = first indicator of overheating plug
- slight discoloration of side electrode = second indicator of overhearing plug
- Some pinking / browning of ceramic insulator = indicator of auto-ignition / knocking


Visual Inspection - Cylinder #4:
- light gray ash on ground electrode = good air / fuel ratio
- slight peppering on side electrode = first indicator of overheating plug
- moderate discoloration of side electrode = second indicator of overhearing plug
- Some pinking / browning of ceramic insulator = indicator of auto-ignition / knocking


ONTO THE NEW - while there's been discussions on other OEM variant plugs (like the RS7 plug), or other aftermarket, in my opinion there wasn't a clear winner.
So, I elected to try the OEM equivalent replacement of the NGK PLFER7A8EG [94833].
* laser welded, dual platinum plug [both center electrode / ground electrode] w/ copper core
* NGK heat range = 7
* specified gap from NGK = 0.031" (0.8mm) - 0.035" (0.9mm)
* bluefox280's gap = 0.028"



Yes, I shorten up the gap on the stock plugs based on experience from my previous MK4 1.8T.
From looking at the original plugs, I'm concerned that if the previous owner did use premium gas 100%, but the plugs are overheating, that a 40K-60K mile service frequency is too long.
Seeing that my GTI only receives premium fuel while in the hands of my ownership, I'm anxious to see how these new plugs react in 15K-20K miles.

Thoughts? Comments? Questions? Curious to see what other DIY owners have to say.

- Erik

You don't have to stay with the cup shaped terminal on top of the plug.

A standard one works fine.

My personal experience, Stage 1 tune at 2k miles and Stage 2 at 5k.

By 20k I had all the signs of tired plugs, rough idle, misfires on cold start, power delivery was not as smooth (hesitations), etc.

Swapped plugs to the cheap Densos IKH24s @.024" and all that crap instantly disappeared.

How much of my plug life was due to a tune and very hard driving, I'll never know, but safe to say 20k was the limit for me.

People also love the RS7s and Brisk Silvers also...I think the Brisk will be my next set.

Hoon said:

You don't have to stay with the cup shaped terminal on top of the plug.

A standard one works fine.

Click to expand...

Seriously? In that case I would have loved to use a much cheaper option plug and change it out more frequently.

- Erik

Hoon said:

You don't have to stay with the cup shaped terminal on top of the plug.

Click to expand...

What other available plugs, with a insulator height of 50.5mm and reach of 26.5mm, can be used?

- Erik

ECS lists these are correct fitment:

https://www.amazon.com/NGK-ILFR7H-Laser-Iridium-Spark/dp/B000HDH19I

Though I don't see them listed on NGK's parts finder.

• Thread Size: 14mm
• Thread Pitch: 1.25mm
• Seat Type: Gasket
• Resistor: Yes
• Resistor Value: 5K Ohm
• Reach: 26.5mm (1.04")
• Hex Size: 5/8" (16mm)
• Terminal Type: Solid
• Overall Height: ISO
• Gap: .024" (0.6mm)

I think this plug is suitable only if you're running colder plugs, as per Stage 2 reqs.

I'm confused----

AspektZA said:

ECS lists these are correct fitment:

https://www.amazon.com/NGK-ILFR7H-Laser-Iridium-Spark/dp/B000HDH19I

Though I don't see them listed on NGK's parts finder.

• Thread Size: 14mm
• Thread Pitch: 1.25mm
• Seat Type: Gasket
• Resistor: Yes
• Resistor Value: 5K Ohm
• Reach: 26.5mm (1.04")
• Hex Size: 5/8" (16mm)
• Terminal Type: Solid
• Overall Height: ISO
• Gap: .024" (0.6mm)

I think this plug is suitable only if you're running colder plugs, as per Stage 2 reqs.

Click to expand...

they the same 7 heat range, not colder. you can tell from the part code

Sent from my SAMSUNG-SM-G930A using Tapatalk

So what is the actual difference between 06K905601D and PLFER7A8EG ?

GeorgeTSI said:

So what is the actual difference between 06K905601D and PLFER7A8EG ?

Click to expand...

The VWAG stamp and lack of ribbing on the insulator.

DiscusInferno said:

lack of ribbing on the insulator.

Click to expand...

Thanks, does that make any difference in practice ?

Also most photos I've seen of either part have no ribbing.

Also according to some sources, PLFER7A8EG replaces 06K905601B, or even C, but there is no mention of 06K905601D. See here Equivalent Part Numbers:
https://www.amazon.co.uk/NGK-Z%C3%A3%C6%92%C3%A2-1-Ndkerze%C3%A3%C3%A2-94833/dp/B00U7WB6WC/

On the other hand, these are sold by Volkswagen (branded) and are 2x the price. But the picture shows plug with the... PLFER7A8EG code No ribs anywhere to be seen.
https://www.amazon.co.uk/Volkswagen-06K-905-Spark-Plug/dp/B00KWGNIO2/

What is the deal with these ? Does PLFER7A8EG = 06K905601D ?

Meanwhile on NGK website

GeorgeTSI said:

Meanwhile on NGK website

Click to expand...

That’s what I saw when I needed to replace plugs 10kish miles ago. Using PLFER7A8EG stage 2 Unitronic and I’m seeing single digit misfires across all cylinders after a long, somewhat spirited highway drive. Any issue with that? No cold start misfires.

First off I’m not an expert on spark plugs but I don’t believe the pink color on the porcelain insulator is a sign of detention/knocking. True detention/knocking would cause some pretty obvious physical damage.

Here’s a good comment from this link - https://mechanics.stackexchange.com/questions/48516/what-causes-pink-spark-plugs

The pink color has a similarity to the "ferrocen" symptom. Ferrocen is an iron-containing anti-knock fuel additive. It causes red, electrical conductive, deposits on the spark plugs. There are cases documented where is was illegally used to increase the octane rating of cheap fuel (google "Firepower ferrocene spark plugs"). According to Bosch (sorry for the German reference) cleaning is futile, you must replace the plugs (and the fuel station?).
Perhaps you want to ask the owner if he uses some fuel additive or prefers a certain brand of "special" fuel at a station where it is spectacularly cheap?
Edit: I also found an additional reference from champion (first picture on the top left)

This is also a good guide which also states a pink hue is due to fuel additives:

https://e3sparkplugs.com/blog/are-your-spark-plugs-talking-to-you/