[gtaccord]

No problem here either with the bosch plugs on two different 335s.

Also there is no such things as "factory seconds" in this case. I worked in automotive at a seal manufacturer. We made aftermarket parts on the same machines using the same materials as the factory original parts. The only difference was typically that the branding was missing and the tools were not customer owned.

It is possible for the bosch plugs to differ from the bmw plugs because the tooling for the bosch plug may not have been updated or they may be a different design revision. In the end, the bosch plug is a bmw design but they may not the most current design.

[Lotus99]

Originally Posted by Dackelone

Yes, there is a difference. Yes, it does matter. Some members run into misfire issues when they use the non-BMW dealer plugs. They end up replacing the coil packs and injectors only to go back and replace the after market plugs with BMW bought ones. For this reason, I would only use BMW bought plugs.

IMO its not worth taking a risk with aftermarket plugs to save a few bucks.

Then again... many guys here use the Bosch(aftermarket) plugs with no issues. But some people do have problems with them. In my mind its not worth taking a chance. I would rather use parts thru my dealer.

The problem is you're drawing a cause / effect relationship here, when there's no solid proof. Any part has a manufacturing defect, for example, including BMW plugs. There's nothing to say the couple of cases you've read about, aren't just that, and had the person replaced their Bosch plugs with a new set, they'd have fixed the problem too.

[gtaccord]

Originally Posted by Lotus99

The problem is you're drawing a cause / effect relationship here, when there's no solid proof. Any part has a manufacturing defect, for example, including BMW plugs. There's nothing to say the couple of cases you've read about, aren't just that, and had the person replaced their Bosch plugs with a new set, they'd have fixed the problem too.

+1

[Lotus99]

If there truly was a cause and effect, I'd think you'd see a lot more issues than the odd few that have been reported.

[matreyia]

Originally Posted by Lotus99

If there truly was a cause and effect, I'd think you'd see a lot more issues than the odd few that have been reported.

Probably safe to say that Bosch non-bmw branded plugs do not get the stringent QC that BMW branded plugs get so their failure rate is higher that OE. But both plugs are close enough that they will work. Thus there are sporadic failure reports of the Bosch plugs. BMW doesn't want a simple thing as a spark plug with their brand association to fail otherwise, folks will just laugh at them for the inability to provide a simple spark plug of proper quality.

[secretsquirrel]

I've been running the Bosch plugs for over 100k tuned. No problems.

[Scottycs]

Unless you can back up your claim, I call BS.

Originally Posted by matreyia

Probably safe to say that Bosch non-bmw branded plugs do not get the stringent QC that BMW branded plugs get so their failure rate is higher that OE. But both plugs are close enough that they will work. Thus there are sporadic failure reports of the Bosch plugs. BMW doesn't want a simple thing as a spark plug with their brand association to fail otherwise, folks will just laugh at them for the inability to provide a simple spark plug of proper quality.

[Milan]

I have nothing to add except that I have the NGKs and will be going back to Bosch/OEM. My car misfires at idle on cold starts with NGK.

[npowered]

I will be going back to OEM Bosch plugs to see the difference as well. I replaced the OE's with NGK 5992s to try and eliminate a source of my hesitation and misfires. No luck. I then replaced all my coil packs out with OEM Bosch (misfires came from random cylinders so I didn't waste time swapping packs between cylinders). Still hesitation and misfires. Learned of walnut shell blasting and had that done for $400. Fixed the issue. All this at 91k miles and I'm the 3rd owner so no idea of what the previous two owners did or didn't do for maintenance or aftermarket upgrades. I have my old Bosch plugs, but at $70 for new ones I'll spend the money since mine could be up to 91k miles old.