billapex

Yes, I did a search but didn't see anything for the C55, only the C32. My question is, how many miles are the stock C55 plugs really good for? I know they're platinum, which they say are good for ~100k miles, but I've always been a proponent of changing platinum plugs at no more than 50k, just for the sake of performance and efficiency.

My C55 has ~56k miles, and I'd just be using aftermarket platinum replacements (Autolite, NGK, etc.). I really see no benefit to spending more than $3/plug on an N/A car.

And is there any benefit to replacing the wires, assuming they're not damaged?

Thanks for any help!

Bill

rockjock

Wires help for a more consistant spark with less interferance (at higher RPM-you may notice a small amount of mis-fire from older/worn plugs, or plugs that are too hot for the car) best bet is to pull a back bank plug and see what it looks like-if its nasty-swap them out!

mkonei

im about due as well. keep me posted on what you find out.

mike

c32used

Even if you went by manufactures specs you'll never find a $3 plug for your high performance sedan I even think regular plug will cost more then $3...also wires enhance the spark so wires will give a better spark delivery and I would change them at your mileage..I already changed my plugs twice and wires once...ALWAYS KEEP IN MIND YOU GET WHAT YOU PAY FOR...GL

Quicktwinturbo

I've always thought s-plugs / wires were good for 100k miles on our cars..
I think i read it on the manual.. Please correct me if I'm wrong.

hooleyboy

Remember you need 16 spark plugs for your C55. There will always be the debate on what spark plugs to get. I would just keep it simple and stick with the stock NGK plug and maybe just go one step colder. I sat for a while debating on what kind of plugs to get NGK, Denso, bla bla bla. I decided to go with a NGK OEM style plug, Only because it is supported well in my local area. I think thats the most important thing... IF a plug craps out getting one wont be hard.

expect to pay $7-8 dollars a plug for a good well respected plug.

hooleyboy

Just seen you are in AZ,... My plugs were on there last leg at 35,000 miles, when they were changed they were a rusty red/brown color from the crap fuel we get out here in AZ... Change your plugs.

billapex

Hooley, that coloring is most likely residue from fuel additives, such as octane boost. Have you used that in the past? It also coats O2 sensors and lessens their effectiveness over time.

I'll most likely use inexpensive double-platinum plugs ($4 Autolites, NGKs, etc.) and not anything like iridiums, as I just don't believe I'll realize any cost/performance benefit. I just want the longevity of the platinum.

I owned a high-performance shop in NorCal for almost eight years, specializing in Mustangs and Vipers, and in all the high-hp cars we built, we used standard, cheapie plugs to make the most power. Platinum offers zero performance benefit, only longevity, and if you're hard on your plugs (i.e. a blown car, nitrous, etc.), they should be changed every 10k-20k miles anyway, so no sense in spending more than $2 a plug, really.

As well, we didn't have any luck with Iridiums on blower cars. Even with a high-output ignition like a Crane HI-6, any boost higher than 10psi would blow that fine-tipped spark out. We always relied on $2 Motorcraft, Autolite, or Champion plugs, even on cars making 650hp+ at the wheels. They consistently made the most reliable and consistent power.

Bill

60n5pt1

Has anyone tried these?

JToups386

Just as a point of reference, I purchased NGK copper plugs for my C55 soon after I bought the car. I've always believed in getting better performance out of a good copper plug rather than the longevity of a platinum or iridium plug. However, everything I had owned previous to the C55 made for a relatively easy plug swap job. Clearly that's not the case on the C55, and it also has 16 plugs to deal with.

When I pulled a couple of my stock NGK Iridiums out at 55k miles, I was very surprised to see the gap was still holding at the recommended .044. I was completely planning to replace all my plugs until I measured the two I took out, and realized there was no need to do it yet. Now that I have 67k miles on the car, I may check them again to see if it has changed at all over the course of a year. If so, I agree with what Billapex said above, in that you don't have to spend $16 per plug to get the Iridiums if all you're looking for is better performance. Cheap Autolite or NGK copper plugs will provide a better overall burn.
However, if you're not wanting to do the job again for 50k+ miles, then you'd want to at least go with a good platinum, which can be purchased starting at about $2.49 per plug on average.

GoPwr

My wife bought a 2005 C55 AMG in March 2012 with about 105k miles on it.

She now has about 119k miles.

She drives it like a granny and recently boasted of a trip from Birmingham, AL to Atlanta, GA averaging 23 mpg !

If the car runs strong (when I drive it) and it is averaging between 17 and 18 mpg around town and gets 20 to 23 mpg on the highway...should I

1) Have a plug bank pulled to inspect the plugs (for potential replacement) ?

2) Just go ahead and drive on!

3) Change them and HOW?

Myself with the proper tools and moral support ? OR

Just pay about $250 labor with my MB specialist plus $8/9 bucks a plug on Amazon?

Like many others, I am on the fence about intervals / performance / preventative maintenance / over doing it when unnecessary

Thanks

c32used

Sounds like MPG is average with everyone if your wife puppies it on highway I can see up to 25/26 if driven at under 60 MPH on highway....if plugs original I'd definitely inspect them...there should be a DIY that can save you on labor charges. I know on C32 the rear ones by firewall are a PITA but not impossible. Try it.

GoPwr

Thanks! C32used

adl320

I'm bumping an old thread, but I just did my plugs and wires yesterday after 84K original miles on the old plugs and wires. I went with the OEM NGK Laser Iridium IFR6D10 plugs and Bosch wire set. The plugs were not horrible looking and the head was very clean - A good sign.

While in there as a preemptive measure we also replaced both valve covers, the CPS, ambient temp sensor and replaced a broken fog light. I haven't done much DIY on the car but this is something I will do on my own next time, even though that will be a long time away. Attached are some pictures of the head and plugs at 84K miles.