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Under 5 years old, under 30k. After $6,400 and 7 months of repairs, this car is done.

TL;DR

• 2021 C63 coupe, bought new, 27,764 miles, all scheduled maintenance completed.
• Since Feb 26 it has had three repair visits for the same misfire. I've paid $6,414.64. It has spent more than 140 days in the dealer's shop, 125 of them on the last visit alone. Every time I got it back, the light came on again.
• The dealer now wants about $14,000 to inspect the engine and about $15,000 more to repair it, nearly $30,000 on top of what I've paid. That would be about $35,400 in repairs on one car, and they can't promise it will be fixed.
• Mercedes-Benz USA denied my buyback request. The arbitration program they pointed me to won't take my case. They offered $4,800 by voicemail and haven't told me in writing what it comes with.
• I'm 100% sure I will never drive or recommend a Mercedes again.

Background: I had a 2010 C63, also bought new, that I drove for over ten years with no real problems. A friend has it now and it's fine. Both cars went to the same independent mechanic. The 2021 was shipped to California right after I bought it.

The log

Feb 26, 2026 · 26,861 mi

Check engine light. I take it in. Codes are P030022 and P030800, a misfire on cylinder 8. They replace the ignition coil for cylinders 5 and 6 and note that the concern is "no longer present." I paid $1,150.91.

March

I spent a few days texting and calling my advisor to find out if the car was done. No answer. When I did get it back, the steering column had been put back together with loose parts, and I could hear it. I emailed a couple of videos. No reply.

May 5 to May 19

Light's back. They do more work on the engine, and I pay $3,473.78. The light comes on again about a week after I pick it up.

May 28 to Sept 30

The car goes in and stays about 125 days. The dealer opens a tech support case with Mercedes, tests everything they can, and finds nothing wrong with the engine itself:

compression, all 8 cylinders: 165-170 psi
cylinder leakage: 8-9% on 1-8, "ok"
borescope: no damage to lining, head, valves
wiring to coils and injectors: ok
intake smoke test: no leaks

They put in a new cylinder 6 injector (it had an internal fault) and clean out carbon. The invoice ends with this:

MISFIRE STILL PRESENT AFTER CYLINDER #6 INJECTOR
REPLACEMENT, CARBON CLEANING AND EXTENSIVE DIAGNOSIS.

My bill was $1,789.95.

July 16

I open a case with Mercedes-Benz USA and ask for a lemon law review and/or a buyback. They say the review takes about 30 days. On July 27 they tell me they can't help with a loaner. The dealer had already asked them for goodwill on my behalf and been turned down.

Aug 10

The case manager writes that he can't say anything about reimbursing repair costs because he isn't a lemon law attorney and the department that reviews cases is "not customer facing." He suggests I ask the dealer to hold off on repairs "for a few more days" until the case concludes.

Aug 12

Denied. The letter says my vehicle's repair history "does not meet these legal requirements" and doesn't say what that means. It tells me that if I'm in California I can use a free arbitration program (NCDS).

The same day there's a voicemail from the case manager: the review "did come back to decline," but "in lieu of the decline" the field team has offered $4,800 "for your inconvenience." That isn't in the letter or in any email.

Aug 17

NCDS says they can't take my case because the car was originally sold in Connecticut. I tell Mercedes and ask what else I can do. I ask again Aug 19 and Sept 10. I haven't had a reply to any of them.

Sept 11 · Sept 30

On a call around Sept 11 I'm told the $4,800 might come with conditions. Nobody has told me what they are. A check arrives dated Sept 11, written on the dealership's account, memo "MBUSA REIMBURSEMENT." I'm not depositing it until I know what I'm agreeing to.

On Sept 30 I get the car back. The check engine light is on and the engine feels jumpy. A few weeks earlier the dealer's plan was a warranty computer replacement after another big repair. After running tests on the computer they've changed their mind: it's not the computer, a cylinder needs replacing. They want about $14,000 to inspect it and confirm, then about $15,000 for the repair. That's nearly $30,000 more, on top of the $6,414.64 I've already paid, and they can't promise it will be fixed. I said no.

Meanwhile

While the car sat in the dealer's shop, their marketing system kept emailing me. "Stay Road-Ready All Summer Long" on Aug 6 and again on Sept 7, and "Reliable Performance Starts With Routine Service" on Sept 1. On Sept 11 I got a request to rate my recent service visit five stars.

What I've paid

If I deposit the $4,800 check, that leaves $1,614.64 not reimbursed.

On warranty

The new vehicle warranty is four years or 50,000 miles. The car was delivered June 2021, so the time limit ran out in June 2025. The misfire started in February 2026, eight months after that, at under 27,000 miles. Mercedes's position is that this puts it outside the lemon law. I'm not trying to argue the law here. I'm asking for a fair outcome on a car that has had the same problem since February.

For what it's worth, Mercedes has published service bulletins for misfire check engine lights on this engine family (M177). One of them, LI07.61-P-070707, is cited on the dealer's own invoice and lists "multiple causes." A bulletin isn't a recall and it isn't an admission of anything. I'm only noting that the dealer followed Mercedes's process, and the misfire is still there.

What I want

Ideally they'd buy the car back. If they won't, I'd like the rest of what I've spent reimbursed, and the inspection and repair the dealer says is needed covered, with something in writing about what happens if it doesn't work. And I'd like straight answers, in writing, about the $4,800: what it is and what it's tied to.

I've sent Mercedes-Benz USA a letter with all of the above. I'll add what they say here.