Model: C350. Mileage: 139,000.
Previous Oil Leaks:
1. Crankcase Breather Cap
2. Oil Cooler.
Both Replaced.

The SA is recommending an engine oil cleaning. He recommends doing so every 3rd oil change.

The car is going thru 1 quart of oil a month. I see no engine oil on the ground.

I checked the cam plugs and they look clean. Some residue but no oil on my hand.

Therefore SA thinks it's burning oil.

Q 1. Is it possible the oil pan seal could be leaking enough so oil never reaches the ground?
1 quart seems like a lot.

Q2, Would you do the oil cleaning service? It seems logical at this point with mileage.

Opinions?

If it’s burning a quart a month, I would be checking valve stems, guides and seals, and piston rings to see if you have something worn/leaking.

An engine flush is not needed in a car with regular oil changes. Actually, it’s really not needed at all.

I bought it as CPO with 48,000 miles. I’ve missed one oil change one time. Not sure how far I went over. I think it was more a time thing.

These cars don’t burn oil as far as I know.

Maybe the valve cover gasket is on its way out.

I’ll update once I hear what the mechanic says.

Thanks 🙏

The mechanic found no leak; he said to come back if it's still using oil.

In the report, they transferred over recommendations from 2019.

Those have been addressed.

I have not been to the dealer in a while but it's still the same lousy experience.

The routine inspection is pretty laughable.

At least I got to drive the 2020 C300 loaner for a few days.

How would you compare it to your car in terms of driving (engine, transmission, feel...)?

Great question.

TL;DR: The C300 is certainly a nicer car overall than mine but there are some trade offs. Keep in mind my car is 11 years old!
So you're talking over a decade of progress. The C300 felt a bit slower but transmission, suspension, feel etc. is certainly a better driving experience.
Would I buy it? Hmmmm. If I got an amazing deal on it, I probably would.

My preference would be a C43 2019 or C400 (specs wise but have to drive it).

First some stats for context. You probably know this but others may not...

2009 C350: Stock is 3.5 L V6, 268 HP with 258 lb-ft of torque.
I had it tuned by OE Tuning who claims 284 Horse with 273 lb ft of Torque.
17 Inch wheels but I'm changing them to 18 or 19 fairly soon. Torn on size but leaning 19.
Rear wheel drive. Naturally aspirated.

Mileage: 139,000.

2020 C300: 2.0 L four-cylinder engine. 255 horsepower and 273 lb-ft of torque. Turbo charged. 19 Inch wheels.
I drove with The AMG line package.
15-mm lower ride height to deliver more precise handling response (source MBUSA)
Not sure if it was 4-matic or rear wheel drive.

Mileage: 22,000 Miles

Off the line, the C300 still feels a bit slow due to the turbo lag and lack of HP. It did surprise me in the 20 to 25 MPH in terms of acceleration. MB has tuned the hell out of it!

Oddly the best mode is Comfort and not Sport or Sport Plus. Suspension was excellent and handling very good. The steering wheel felt a bit stiff. Then again I'm riding on 19" wheels.

Suspension: The C300 is certainly superior. I replaced mine with Bilstein B4 and I'm not satisfied. So maybe B6 or maybe H&R springs...

C300 Transmission: 9-tronic. Fast and smooth. C350 is the 7G I believe. The 2020 C300 felt like it had a better gear box.

The only complaints are the turbo lag and the lack of power.

Was I blown away? No but I was impressed with what they've done with a 2L engine. The suspension is a nice upgrade and surprisingly good.

you need do this , get 1 bottle leakstop , and one engine teflon treatment, can warrant your engine oil use will go down alot

https://www.solidstart.com/Solid_She...SolidSheet.pdf this is for soften up seals, and most important valve seals, my car sl55 not filled oil in 20 month sinse oil change.

then also you need this., 1 bottle . add both in cold engine after shake well ,and go for a longer drive, let me know how well you see improvment.
https://www.solidstart.com/products/engine/t132/

if use 0 40 oil, next time , go for 5 - 40 . i have a tread in R230 group about protect engine, and oil use .

20 Months since your last oil change? I thought oil still degrades over time...

I just changed the oil — 5W40 Oil. Shouldn't this be done close to an oil change or does it make no difference?

if you changed oil , just suck out little what you have in there, and add the 2, they will slowly clean the system also.

if you want take it all out , then do engine internal wash , is 30 min wash on idle ,then out with oil and filter. Then add the stuff.

you can read about tings here, and look the cleaning stuff also . https://www.solidstart.com/products/engine/t132/

You think the 9G equipped C300 is slower than a 2009 C350? That would be.. surprising. Mercedes quotes those cars at 0-60 in 5.7, faster than even the 302hp C350s. I've had them as loaners as well and they are pretty quick, but they do deliver power completely differently than NA V6s

And just to add to this as I see there’s been a recommendation to put “SolidStart” in your car.

Don’t.

Especially when reading this:

• Formulated bonding agents are designed to fuse to engine’s friction surfaces to engine life.

If these products actually worked, you’d have every mechanical shop using it like it went out of style.

I would never put something in my engine that’s going to “bond” to the internals to cover up the leak/issue.

There’s an obvious oil burning issue, using SoildStart to try and cover it up is not going to make it go away.

Did I say my car is faster? Absolutely not. That's not what I said.

I was asked "how it felt."

It felt a bit slower off the line. Then again I had the car for less than 2 full days. But as I indicated they are two different engines and transmissions.

My car is tuned and with turbo there is "turbo lag" — at times. Is there a huge difference in terms of power? Not to me...

Is the 2020 C300 a nicer car overall and better? Yes, of course. Am I going to buy one? Unlikely...

Did I say that's what you said? I asked if you thought it.

No need to be so defensive.

Agreed. I'd rather do it properly. If I had a turbo engine I could see oil consumption. Hopefully not the head gasket...

Are you noticing oil coming from the tail pipe? How about smoke? Does the car smoke in cold start situations or hard acceleration? The M272 is not known to burn oil. I change the oil when the message pops up which works out to 14,000kms or annually and the oil on the dipstick just before I change the oil is the exact same level at the middle dot.

IF YOUR VALVE seals is tight, oil use go down, is a no brainer. cover up he he he . must be reason microwaves have warning on them, not dry your pet in it . in USA. Sorry i have too be so hard on you, but low knowledge and bastant end result without tryed ,is just dumb.

If you have not used, or have any knowledge what you talk about , maybe read yourself up on the subject . For engine,get most power out of one engine, internal friction is heat, your fuel goes in create heat because of friction. , Ask any AMG owner what oil temps he read hard driving , i read 105 C now 221 F , doubt you will find any that has so low temp under hard repeating accelration in 31 C / 88 F outside temp , heat on the sunny road on top of that , with no wrapped headers .

I talked to many mecanic , and they dont know mutch about tings to improve ,and save their customers money , they want customers to come back as often as they can to make money . QMI engine teflon i used sinse 1995 , with extreme good results, probaly saved me small fortune in repair as hard as i drive .

Also maybe you know that rubber seals ,is made out of rubber , and they dry out by age ,and do not seal as they should do, this result is oil pass the rubber valve seals and end up as deposit in the head chamber ,and blue smoke out the exhaust pipe. My sl55 ,2007 have one bottle of this stuff, https://www.solidstart.com/products/engine/t100/ Same as Full trottle Liqseal , and it does not use oil ,a engine that use normaly 1 q per 1000 - 1500 km / 625 - 932 miles . I not filled oil in 6300 miles on my car , how you explaine that ?

My personal mecanic use this stuff in all his engines, because he seen result on my cars. and say fiuel use is down on SL55 , and his Diesel engine c30 AMG do not use oil between changes , next week we will add this leak stopper, to stop his slowly drip from rear main seal. on the 55 have another mecanic frend, he run a mecanic shop ,and have E 55 ,2004 , drink oil like hell, will talk him into do the same, i had same engine in my older sl55 2004 , and teflon treated engine, not leak stopper added, oil use went down about 4 times.

Ceratec with Boron does same job, reduce friction and wear , they use alot money on advertising , and everyone that use it ,se result. does the mecanics want you to add that ? i am all for this stuff also. reduction wear ,and friction will save everyone money in the end.

Sorry, your recommendation was and still is terrible.

I don’t quite understand what you’ve posted here as it seems you were frustrated when typing but please don’t get mad when others call out your poor advice.

I really don’t care what your backyard mechanic has to say about dumping SolidStart in engines to cover up issues, sounds like you need to find a new mechanic.

I was a heavy duty tech for almost 7 years, I think I’ll trust my judgement over someone’s poor recommendation.

And just one more thing to add to bring some humour to this thread;

Do I really have to try SolidStart to know it is ****?

My car is back in the shop for a suspension rattle from the driver side. This time I have a C300 2020 with 18" wheels instead of 19" wheels.

The loaner is faster off the line than my C350 but not a big difference.

I’m not that surprised considering bigger wheels add weight and use more power.

I have to wonder what these cylinder blocks weigh?

The 18” don’t look terrible. Probably look better if you lower the car.

With 19" flow formed, Perhaps that might compensate.