Depends on how you define "not the best plugs". If they are from a reputable manufacturer, and are the wrong heat range or of a poorer design, you can impact fuel economy and power as well as total plug life. If they are far out on the heat range there are more serious consequences. If they are not from a reputable manufacturer, no matter how they are labelled, the potential consequences are a broken electrode and resulting catastrophic engine damage.

NEW BMW Recommended OEM Spark Plugs
 

According to RealOEM.com there are different BMW OEM spark Plugs being recommended now (part number #12120037607). Just to confuse everybody some more. Any thoughts on this from anybody?
RealOEM.com * BMW E53 X5 4.4i Ignition coil/spark plug

great inputs guys, but i am having a code p1354 which says "misfire during start cyl 7" which prompted me to think of changing my spark plugs since i couldn't find any info concerning this code. So i removed the spark plug and i noticed it was a NGK spark plug stamped BMW with the same part # BKR6EQUP made in japan with a code K92R written in smaller letters. Right now i'm thinking whether the regular NGK BKR6EQUP form the regular part store will work. I'm not sure if that BMW stamp is for it to sell for $21.00 or is there really a difference in performance considering the mileage form 50K to 100K. So for i'm still not sure what brought in that code. Also the plugs i took out was form my 03 4.6 and they still look good and clean. Tell me what you guys think!!

Hopefully the link will work for you, but I just ordered 16 of Iridiums for my 740iL and X5 from Autoparts Titan for $111 shipped, so half that for only need 8 of them is still a damn good deal shipped t your door.

ebay.com/itm/250854888590?ssPageName=STRK:MEWNX:IT&_trksid=p398 4.m1439.l2649

I have tried ngk and bosch: same performance . But ngk didnt last as long as the bosch: ngk ( 20k miles but bosch : 60k+

Bosch FGR7DQI
 

Just installed 8 of these from Bosch. Engine purrs.. no problems. Very easy install compared to others I've done.:thumbup:

I installed the NGK's today, pretty easy job.

OK, I went to realoem.com, entered the last 7 digits of my car's VIN number, and it came up with the four different part numbers, two Bosch, and two NGK. When I enter any of these four part numbers in the part search function at Autohausaz, I get the following three choices:

Your Parts Search Returned 1 Part(s)

Does this imply that any of these three plugs is acceptable? If so, why on earth would I buy the $9 plug over the $3 plug? I'm sorry, but $9 (or $15, or $21) for a spark plug is ridiculous. As long as the specs (heat range, dimensions, etc.) match, why should it matter?

The 4-Electrode type is the one you want to use as it is similar to OEM. The Bosch ($4.23 one) is really cheap. I have the $9 NGK installed (price difference compared to the Bosch a couple of years ago was very similar) and it's been running without issue for the last 20K miles. If you need spark plugs, I would just go with the Bosch 4-Electrode and be done with. And if it dies within the next 50K+ miles, then just replace it with another set as they are not very difficult to replace. As long as the heat range is similar, you won't be able to tell/feel the difference in performance between the various plugs. I can't believe there are so many threads and/or discussion on a simple spark plug. Guess it's the same with motor oil...everyone has their favorite theory.

"As long as the heat range is similar, you won't be able to tell/feel the difference in performance between the various plugs. I can't believe there are so many threads and/or discussion on a simple spark plug. Guess it's the same with motor oil...everyone has their favorite theory."

dkl,

Thank you for such an informative and, above all, sane post. With all due respect, I couldn't agree more that a 9-page discussion about something as simple and borderline inconsequential (relatively speaking) as a spark plug is just goofy. I own a '92 Porsche 968 that I'm converting to a track car, and a few years ago, NGK Iriduiums became all the rage on the 968 forum, so I drank the Kool-aid and bought a set. Couldn't tell an iota of difference compared to the Bosch Patinums I had in there before. I think I'm going to pull one of my plugs (the X5 has 97K miles and is running flawlessly), look up the specs on it, and buy the least expensive plug I can find that comes closest to matching the specs. I'd subject myself to a 12-hour marathon of The Kardashians before I spent anything near $100 on a set of spark plugs :yikes: