Teachaman

It's time for new plugs for my 2012 GL450.
Lots of options. Any brand advice? Bosch?
Figure that I might want to replace the coils as well.
It runs fine, but I figure that after 160k, it might be time and it doesn't look too expensive.
Once again many options. Any suggestions on a brand? Bosch?

Max Blast

Whatever you do don’t throw Chinesium coils on there. OEM or Bosch for both coils and plugs.

eric_in_sd

If you peel up the Bosch label on a coil, you will see "Delphi" underneath.

Teachaman

I tried the Chinesium in my Expedition. The good ones were even more than the ones for the Mercedes. They are great, provided you carry a few spare ones, the right sockets, and an air compressor.

DennisG01

If it's running good at 160K... put the exact same brand/model of plugs back in.

Personally, I wouldn't do the coils yet - but the same premise would hold true... if they're going good at 160K that that right there is pretty strong evidence to use the same kind.

Sorry - I can't help you with specific recommendations, though... my car doesn't have spark plugs

eric_in_sd

I did some research on how the coils work. I think it was GM, but could also have been Ford, that put control of the firing parameters in the coil. The ECU would just send a trigger signal. In these coils, the ECU sends the entire switching current. It actually becomes a weakness of the ECU: the driver chips fail, presumably due to over-current or excess heat. It is sensible to offload the circuitry to the coils, which are much cheaper to repair than the ECU.

This is also why I suggest resistor plugs might be preferable, as they would limit the current flow in the spark, probably stressing the coil and spark plug less.

Anyway, that is probably the explanation for why your Ford coils cost more. The MB / Bosch / Delphi coils are "dumb", despite having four pins.

Coil failure is actually relatively benign. The ECU shuts down the fuel injector to the one cylinder. If you want to eke out life from the coils, just carry with you the coils and the tools, which are not many, to replace the coils. But since replacement coils are all of about $25, I'd be tempted to change them all on a preventive basis.

I had one coil fail at about 120k; then, when I was struggling with ignition issues, one failed right after another. I suspect the tired coils were being overstressed by the ECU.

If you have a misfire failure, make sure to clear the error (CEL) after replacing the coil, or you will have to suffer through drive cycles before it clears on its own.

chassis

Always OEM purchased at the dealer for electrical parts.

Max Blast

You’re not wrong

EWT

Just changed plugs, and I noticed my ML has Delphis with a MB logo on them.

DennisG01

What always goes through my head with things like this is... "But, does Delphi (or whoever) make it slightly different specs for MB?"

Maybe, maybe not. But it may be what's on the inside that counts. Unless I'm 100% sure that a less expensive option is just as good, I'd rather pay a few extra bucks than chance doing it again and now paying twice. Besides, when you spread the cost out over 160K miles...

But then... maybe I should stop listening to myself!

BlackML550

I replaced the original MB plugs with platinum NGK plugs and after 40,000km Ive re-gapped them once and they run just as well, if not better than the originals. I didnt go for Iridium plugs as they seem to simply last longer rather than give any noticebale benefit to performance. If you go down this pathway, DO NOT buy them over Ebay. Most are fraudulent copies and its easy to get duped. I did and it was only a small detail that I noticed that gave them away. Buy from Rock Auto or FCP Euro or similar and youll be guaranteed.

DarthVaderpa

FCP offers Bosch (OEM) as well as "Genuine Mercedes" spark plugs and ignition coils. And they come with lifetime replacement guarantee.

eric_in_sd

It is hard to say. I would emphatically steer clear of a Chinesium coil. Delphi is a major OEM maker, though, and I am skeptical they would endanger their reputation like that.

The same would hold true for Bilstein. They could make suspension components to lesser standards than those with a MB sticker on them, but it's not what I would do.

The MB coils are very simple, by the way. They are "dumb", literally just a coil inside packaging. There isn't much finesse involved.

DennisG01

I was thinking more along the lines of it being made to a higher spec (or slightly different specs, anyways) for MB use. I'm probably over thinking it, though...