[mike sevel]

'08 328i. Bought certified 4 yrs. old. Replaced original plugs, DENSO IRIDIUM SK20R11 at 50K miles with NGK R5. Now at 90K+ thinking about replacing the plugs as MPG is dropping and I use Techron for the injectors. Coils replaced at 50K miles.
Now I noticed that the thread length of the original SK20R11 is appx. 5/8" and the NGK R5 thread length is a full 1". No piston slap and car running fine for 40+ miles.
What plug would you suggest and thread length?
Thanx,
Mikey

[mainbearing]

I am not sure what NGK R5 is. But SK20R11 does not sound like a correct plug. It is not listed for the application on Denso's catalog.

Denso's catalog lists SK20HR11, and NGK's catalog shows a platinum plug PLZFR6A-11S (NGK #5987).

Looks like BMW went cheap and switched to platinum with a shorter (60K mile?) interval? My 07 gets NGK long life iridium ILZFR6D11 (NGK #1208).

Besides the spark plugs upstream oxygen sensors should be considered if they have >100K miles.

https://ngksparkplugs.com/en/part-finder
https://www.densoautoparts.com/part-...ehiclePartNum=

[zerowaves]

I bought a set of NGK 6619 plugs and I've put about 500 miles on them since last week, no issues at all.

[tlow98]

Just out the stock spec ones in there. No reason to do anything else if looking for mpg…

[The Nightman]

Take your pick:
BOSCH FR7NPP332 - double platinum, 80k mile life
NGK PLZFR6A-11S - double platinum, 90k mile life
NGK LZFR6AP11GS - platinum center only, 40k mile life

[jadams161]

Never heard of an NGK R5?? Is that a mower plug..lol.

Put the correct stock Bosch plugs or upgrade to NGK Iridium. Replace the coils too with Eldors. fcpeuro.com

[mictang]

I actually did some research on this, if you are running the updated coils (Delphi 12138616153 / Bosch 12137594937), these two NGK options are the OE plugs, I personally run 11S because weirdly it's cheaper than 11GS in my region.

Originally Posted by The Nightman

Take your pick:
BOSCH FR7NPP332 - double platinum, 80k mile life
NGK PLZFR6A-11S - double platinum, 90k mile life
NGK LZFR6AP11GS - platinum center only, 40k mile life

The NGK ILZFR6D11 is the Iridium option that came on early model years and has a different height than the later ones, I wouldn't run them with the newer coils for this reason. Double platinum should have more than enough useable life anyway.

Reference:

12120032137 = NGK ILZFR6D11
Center electrode: iridium size: 0.6mm
Ground electrode: Platinum
Overall Height: JIS (53mm)
Longevity: 100k Miles

12122158253 = NGK PLZFR6A11S (up to 2009)
Center electrode: Platinum size: 1.0mm
Ground electrode: Platinum
Overall Height: ISO (50.5mm)
Longevity: 90k Miles

12120037663 = NGK LZFR6AP11GS (since 2013)
Center electrode: Platinum size: 1.0mm
Ground electrode: Nickel
Overall Height: ISO (50.5mm)
Longevity: 40k Miles