What spark plug do you guys recommend for my E53 4.8is?

[BMW-x5-48is]

Originally Posted by StephenVA

There are two suppliers to BMW on the X5 NGK and Bosch.
Most of the US cars came with NGK out of the factory.
The OE plug is NGK, Part Number IZFR6H11 Stock No. 4294 OE Laser Iridium
The upgrade plug (was NOT available way back then) is Iridium IX Part Number ZFR6FIX-11, Stock No 6441.

More Information on these plugs NGK Spark Plugs USA

There are some who say use the multiple side electrode plugs like NGK 3199 More Information for NGK 3199
This is a step backwards in plug technology and the side effect is a slight harder start when cold due to the shrouding of the center of the electrode.
I have tried both and I would stay with the single fine wire center electrode for all around performance.

There are some who swear by a brand (pick one). Having worked for Champion Spark Plug Champion Spark Plugs for a few years, the real issue is heat range compatibility and center electrode materials and design. When the fine wire ones where introduced way back in the 80's the increase in performance was measurable (.5 sec on the qtr mile, 1 sec on a road track, and 2 MPG on a steady fuel economy run). Now days every car has them OE. (Except E39 M5 the engineers found the multiple side straps last longer so that is what we screw in there.)

Bottom Line: Screw in the Iridium IX Part Number ZFR6FIX-11, Stock No 6441 and you will be happy.
Where to buy? Try RockAuto Parts Catalog if you can not find them locally as I see you are in Hong Kong China.

Thank you for posting this. I found it super helpful today. Just purchased a set of the NGK ones... the Bosch ones are horrible - today I got misfire bc of extreme humidity - its been raining past 2 days - but among other problems the spark plugs are just not as good as the original ones... I replaced the original ones at 70k - they were fine!! but i replaced because i didnt want them going bad on me.. the god damm new bosch ones have been in less then 10k and already causing CEL to come on, which it has never in past 6 years i owned the car.. so I bought the NGK ones.. Thank you so much for the links and helpful info.... I also noticed a "racing version" of the NGK plugs.. -> https://www.ngksparkplugs.com/produc...ng-spark-plugs -- these any good?

Also as far as the NGK ones - if the original ones were the LASER ones - and they last longer - why would the IX ones be better?? I am following your advice and ordered the Iridium IX, but what is the true advantage of Iridium IX over the original laser ones? see below --

NGK laser Iridium spark plugs provide superior ignitability and long service life. Smallest tip diameter available Iridium / Platinum surfaces ensure slow wear rate providing stable idle, superior anti fouling, improved fuel efficiency and lower emissions. Plug features include: laser welded Iridium center electrode tip, platinum disc welded to backside of ground electrode for long life, trivalent Metal Plating for superior anti-corrosion and anti-seizing. All of these features provide: faster starts and quicker acceleration, Better fuel economy and lower emissions

NGK Iridium IX are designed specifically for the performance enthusiast. Each plug offers extreme ignitability, improved throttle response and superior anti fouling characteristics. Fine Iridium tip ensures high durability and a consistently stable spark. The Iridium alloy has extremely high melting point, perfect for today's high-tech, high-performance engines. Plug benefit include: outstanding acceleration, high fuel efficiency and durability.


So I guess the IX are more performance based?? good for 4.8is performance engine?? where the laser ones are good for your grandfathers bmw?? where all he cares is about service life??

[X53Jay4.8is]

NGK definitely works better and last longer in these V8 X's than the Bosch.

[StephenVA]

I am glad to read that all that detail provided some value to your questions and concerns about plugs. WAY too many people pull out the plug, read the part number and brand and screw in a new version of what was in there with no thought on how the technology has moved on from the date of manufacture. Your experience with Bosch in our applications was the same as mine as they produced poor idle quality, and even worse tip in acceleration in my own 4.8is. I used their multi prong plug +4 , which sucked to put it mildly. I ran them for 30 days approx 600 miles max. Trash canned them.

The NGK plugs for your X5 4.8is is ZFR6FIX-11 Stock no. 6441 IridiumIX.
This plug will give you better idle and a longer life then the plug that came on it OE.

The LASER version of Iridium was the OE plug designed back 10 years ago. It will not last longer than the IX plugs. It will last longer than conventional plugs ( old copper core versions).

The Race plugs are just that, plugs that dissapate heat better and are designed to operate in high RPM only. They foul very quickly at idle and part throttle which is why when you watch any car race whenever a car is in the pits they are constantly blipping the throttle to keep the plugs clean. This is especially true on carb applications as in order the run at high RPMs the cars run overly rich.
Bottom line: do not buy them period for street applications. I used to keep a set of "colder plugs" in my shop just to run on race nights in my big block Road Runner. Then I would sneak back home and replace them for the morning drive to school or work. I drove that car approx 5,000 mile 1/4 mile at a time.

[BMW-x5-48is]

Originally Posted by StephenVA

I am glad to read that all that detail provided some value to your questions and concerns about plugs. WAY too many people pull out the plug, read the part number and brand and screw in a new version of what was in there with no thought on how the technology has moved on from the date of manufacture. Your experience with Bosch in our applications was the same as mine as they produced poor idle quality, and even worse tip in acceleration in my own 4.8is. I used their multi prong plug +4 , which sucked to put it mildly. I ran them for 30 days approx 600 miles max. Trash canned them.

The NGK plugs for your X5 4.8is is ZFR6FIX-11 Stock no. 6441 IridiumIX.
This plug will give you better idle and a longer life then the plug that came on it OE.

The LASER version of Iridium was the OE plug designed back 10 years ago. It will not last longer than the IX plugs. It will last longer than conventional plugs ( old copper core versions).

The Race plugs are just that, plugs that dissapate heat better and are designed to operate in high RPM only. They foul very quickly at idle and part throttle which is why when you watch any car race whenever a car is in the pits they are constantly blipping the throttle to keep the plugs clean. This is especially true on carb applications as in order the run at high RPMs the cars run overly rich.
Bottom line: do not buy them period for street applications. I used to keep a set of "colder plugs" in my shop just to run on race nights in my big block Road Runner. Then I would sneak back home and replace them for the morning drive to school or work. I drove that car approx 5,000 mile 1/4 mile at a time.

Your the man!! Thank you so much for this valuable info! Im glad I ordered the IridiumIX.. They are coming tomorrow, right in time for the weekend project. I will swipe them out this weekend.

Thanks for the helpful info

[StephenVA]

Tips- Just make sure you double check the gap and add a DAB of anti seize to the plug threads before install. Install on a cool - cold engine (when you can rest your hand on the engine head- it is cool!)

Some plugs now have a coating on the shell that acts as anti-seize but take no chances. As long as you just have a dab on the threads you are golden.

[BMW-x5-48is]

Originally Posted by StephenVA

Tips- Just make sure you double check the gap and add a DAB of anti seize to the plug threads before install. Install on a cool - cold engine (when you can rest your hand on the engine head- it is cool!)

Some plugs now have a coating on the shell that acts as anti-seize but take no chances. As long as you just have a dab on the threads you are golden.

Will do 100%... Ive been coming accross the check engine ligh briefly flashing for 5-6 seconds and turning off, not to return later in the day... this only happens in morning, after 8-10 minute drive, on the exact demm street everyday, the light will flash for few seconds and turn off and it will not return or turn again during same drive, or even during return trip, only in morning.. today happened again.. Later I turn car again to go home after work, and light never returns, until next morning, 8-10 min into the drive... I dont know if its misfire, as engine sounds good, so what else could it be? first of all, this started to happen when I filled up my whole gas tank at a gas station, right after 2 days of rain.. So either 1.) Gas is saturated with water/dirty 2.) One of the BOSCH spark plugs going bad (they known for that) 3.) or maybe I need to replace my aging gas cap? .. I noticed its a bit worn out..

I dont know what is causing the light to flash, but will start with spark plugs as i wanted to get them done for a bit, and in mean time im burning off rest of the gas from last station, so I can fill it up with new at another, and lastly maybe will buy new gas cap, to see if the briefly flashing and turning off for good check engine light goes away.

[fishhouse4]

Digging up an old one here in hopes some of you guys who have posted previously can offer some advice.

I recently replaced a set of old Bosch plugs in my 06 4.8is with the NGK 6441 (ZFR6FIX-11) plugs as recommended here.

I've got some weird vibration, rough and loud idle going on after changing plugs, belt and new valve cover/timing cover gaskets.

I've made sure they are gapped to the recommended .044 (according to the specs) and torqued down with antiseize on threads. All coil packs on tight and no engine codes. No misfire or stutter...just a really rough vibration that rattles the whole SAV at idle. Gets better when you give it throttle. Like you're sitting on a Harley kind of vibration.

Just trying to retrace my steps and triple check all variables. My local indy shop said to put back some NGK or Bosch original part # plugs as the first step of troubleshooting.

So that has me second guessing my choice in plugs.

Some of you are running the newer style 6441 Iridium IX plugs for sure?? What did you gap them to? Any input would be appreciated!

[jcp240z]

You do not want to use dielectric grease on the threads. That acts as an insulator and could cause misfire. You need to use anti-seize, which prevents the threads from seizing but will still conduct electricity.

[fishhouse4]

Originally Posted by jcp240z

You do not want to use dielectric grease on the threads. That acts as an insulator and could cause misfire. You need to use anti-seize, which prevents the threads from seizing but will still conduct electricity.

You are correct. Now I remember the grease we put on plugs being gray in color - so that was antiseize. The dielectric we used on all the other wired connections was clear.

[jcp240z]

have you replaced the boots on the plugs? If they are old you may have caused some minor cracking which you can't see, but causes misfire when the were pulled.