Odd Piggy

Let me paraphrase from a Chinese national co-worker from about a decade ago:
Be very careful buying high tech from China. We [the Chinese] can make anything that Europe or the U.S. can and do it for less because labor is low cost in our demand economy. But quality goods require quality materials and testing. These things are not cheap even in China. Some Chinese companies produce look-a-like good which has neither. It is junk to sell to unsuspecting customers. Buy our goods only through organizations that have the resources to do testing and hold the manufacturer accountable.

m00nd0gy

Exactly. I don't trust anyone, even FCP, napa, amazon, walmart, or Advance auto, any of them. Just take your chances and hope for the best.

Mmr1

Fcp is different , and yes their warranty works, I returned a strut a year later, and fluid and pads I did not use. Those guys give you plugs by using your VIN ! They are not Autozone , which is full of Chinese crap and no real warranty .

m00nd0gy

Here is the pics before and after . It is idling better.

Silver Shadow

The electrode looks worn and the gap is huge on the old plug.

m00nd0gy

IMO they're all the same. FCP just charge more; making more profit, unless their products have a manufactures hologram. It's all coming from same sources.

Silver Shadow

Their prices are higher because they lifetime replacement for everything. If you want to send back your used motor oil, they'll reimburse the cost of your new oil. Brake pads, wiper blades etc.

MBKLUE

Something seems "off" with this photo. Maybe it's the angle and close-up nature of the photo but the plug in the top photo seems to have a greater diameter and the deformation of the crush washer is much different between the two. With the top plug the washer is deformed in a cone shape and on the bottom plug it's crushed in a flat manner. Gives me the impression they did not come out of the same brand engine or engine series.

MBKLUE

I'd prefer lower prices then or at least the option to select between higher price with return replacement option or lower price with no return option.

Mmr1

The top plug has the iridium tip, as well as a different washer . Two different plugs. The bottom plug is a cheaper plug that won’t last as long and might not have ever fired properly! the gap is way out of spec , it’s to large.
no wonder your running better, even with the photo not showing correct perspective , I think I’m seeing a gap to large and out of spec, ( measure it) that alone would cause misfire. The new plugs will last longer.Another thing I notice is the old plug is either to cold, running to rich. Or it’s oil blackened . It was not burning clean. I would check the plug specs to operating temp . It could be a worn motor. Air filter, or other things

. The old one may be a Bosch but it’s not Iridium or Platinum, it looks like the cheapest plug they make a 40000 mile plug. Take a better photo and tip closeups. Burning black isn’t correct. Do you burn oil?

m00nd0gy

Not burning oil. I check oil during long drive from Canada to Florida. Before the swap, the car ran well, just slightly rough in drive with brakes on, the gap was checked before installed 6 years ago, it appears the electrode burnt down overtime. Could be lighting for pic. I will post a better pic.


Old GLK350 Spark plug, appears darker in pic. It's actually tan.

m00nd0gy

Summary: So far the Autolite AI 5702 work great, factory gap .04, I gapped them to spec .032. The idle is smooth in drive with brakes on, problem solved. Coils are still original. The original rubber boots looked like new, maybe they're sill good. But I still changed them out. The air filter was also changed. Total about 1 hour DIY. I normally drive in eco more. I need to drive it in sport mode next. Thanks for all the input and feedback. Happy with results.

m00nd0gy

Good observation. The top plug washer is not crushed due to the fact that it is the "before" installation, it's brand new out of the box. The bottom plug is removed from the engine "after" use, about 100km. Thus the crushed washer.

MBKLUE

Only 100km on the bottom plug or did you mean 100,000km? It looks to be in rough shape.

Mmr1

It is burning rich , or cold . Maybe the old plug was the wrong temp rating . Did those new plugs say “do not gap” ? Because they are known to crack

WRC-LVR

hmmm did you mean the plugs came gapped at .04 and you gapped them to .032 as the MB spec for your car?

If those are really iridium , They come pre gapped for the application/motor/car. You are not supposed to gap them !!!! Sounds more like the AutoLite is a generic replacement meant for several engine / car types....IMHO

Per other posts, your car is running better because it has the correct gap now. I would not like to see the black soot you are showing but pull the easiest plug in about 1000 km and see if it s running cleaner. Also if you havent already, scan the car for codes and please change the air filter for a quality MB or OEM made for MB.

Re the boots, if they look great on outside then ok, however they need checking inside where the plug fits. Check for corrosion. replace boot if any found. Also check the old plugs. If there is any carbon tracking down the ceramic part of the plug, change the boot. In high energy coil on plug systems, the spark can flash over down the ceramic to ground, this causes misfires too. this usually occurs due to oil or grease on the plug body during install or leaks onto the boot. Most prevalent when under load at part throttle or when tipping in trying to pass someone.
Eliminate this by using a bit of dielectric grease on the ribs of the plugs to prevent electricity flashing down the ceramic body.

m00nd0gy

Yes, the old plugs are not iridium, most likely platinum, in rough shape but they are not black as per pic, they are tan. Mostly highway miles from driving to south Florida from Canada. I noticed the electrodes do wear down overtime. I'm a retired engineer looking for things to do. I would not recommend waiting until the max life of anything to refresh. Especially, DIY basic maintenance.

habbyguy

While lots of plugs are supposed to come pre-gapped for a particular application, ALWAYS check the gap before installation. Many things can happen between manufacturing and installation that can change the gap, and it takes just a couple seconds to check it.

And FWIW, it wouldn't bother me a whit if the factory gap was a bit different than the car's spec, simply because I do check it, and adjust as necessary.

Also, I've always had fine luck with Autolite plugs, though I almost always use NGK or Bosch since I've been on a long run of Yurrupean cars. ;-)

Odd Piggy

@m00nd0gy You’re fine. I usually stick with the spark plug that the manufacturer used when I can, but was forced to switch when OE spark plugs were no longer made for our M112 engine. Mercedes had a recommended replacement, but I used what I could easily get. That Autolite spark plug comes pre-gapped at 0.044 inch. Autolite’s recommendation is to re-gap for the specific application.

m00nd0gy

The most popular fake plugs are Bosch and NGK, the box says Made in Germany. The biggest disappointment, spend top $ for fake plugs. Good luck!

m00nd0gy

You really trust your possible fake plugs made in Germany to have the exact gap as per spec without checking them. Best to take them out and verify the gap is correct.

Mmr1

You need to read up on Iridium, most say, as mine did , DO Not gap. That’s because the tip is so thin cracking is normal and the tip ends up in the motor ! They should be factory gapped , they are not the normal old style plug, you had the wrong plug in there before .
just be careful, since you made it smaller I hope you didn’t hit the electrode .

m00nd0gy

I did read it. FYI The iridium tip is not gapped. It's the bent part. Plus it's very hard, not to be touched. Since you didn't, you should remove your plugs and check your gap.

Mmr1

I gapped mine , I didn’t read the “don’t do” before I did it . Mine were real close . At 75000 I noticed no benefit over the old plugs . But now they are new .

PACIFICMAN

The logic behind doing the plugs on schedule is allegedly that going longer makes them more prone to seizing with the assorted problems. I did mine "late" at 90,000 miles and they came out without incident, also, they looked new.