Kelvin Bellrose

I just found out that the direct injection engines will eventually have carbon deposit problems on the intake valves. Is this a problem in the 2012 C350? Does anybody run a catch can in the pcv circut? How about just dump the pcv to the ground like the old days?

superangrypenguin

This is a topic I know too much about.

Fortunately for you and fellow MB owners you should be fine. No need to run a catch can either.

MBs air oil separator does a good enough job such that the oil that is on the intake valve reaches a steady state and doesn't cause any performance issues.

Do your oil changes with the approved motor oil and you'll be ok.

Adi-Benz

Did you buy a DI S-class yet? Lol.

superangrypenguin

Debating between that or the A8. Should know very shortly.

Kelvin Bellrose

That's a huge relief.

Adi-Benz

Save yourself for a 2019 facelift

superangrypenguin

For the A8? Yes, that's why I'm waiting. The car is right around the corner (this month).

iamkimosabi

I like how you guys used this guys thread to discuss what cars whos gonna buy when and where lol.

Do the DI cleaners you buy at autozone work?

superangrypenguin

What type of cleaners are you referring to? There's a ton.

Kelvin Bellrose

I don't mind if my thread gets hijacked, it's all good.

Any kind of fuel treatment won't help because it's injected after the intake valves.

superangrypenguin

Incorrect. Redline SI1 has a very high concentration of PEA (phosphoetheramine) and it's one of the few, if not the only, fuel additive that survives combustion, and would travel with the unburnt oil residues back through the PCV for combustion again. That survival of the fuel additive is purported to be useful in cleaning intake valves, or at least helping with it.

The only problem with Redline SI1 and such is that you can only run it a tank or two before an oil change. Due to the properties of that fuel additive, you don't want to run it at every fill up as some of it does end up in the oil (this is normal, just like fuel dilution, to a minor extent) as it does lower the flashpoint and increase the volatility of the engine oil.

Kelvin Bellrose

teksurv

My wife's 2012 SLK 350 has the same engine and is going strong. I had a 2006 Audi A4 with DI 2.0 FSI and while I loved the car, it would need carbon cleaning every ~60k miles. MB also uses a multi-spark system, hoping that contributes to carbon free valves.

superangrypenguin

The latter may, but you are a brave brave man with that 2.0 FSI motor. Not only does it have serious carbon intake valve buildup issues, but the cam follower is a flat tappet design. If that gets punched through, then you'll need a new HPFP. Also, that motor is prone to systemic and repetitive coil pack failure. Don't get me wrong, I loved driving that car, but it was a nightmare to maintain so sold it for the W204 and it was a great decision. I miss that B7 A4, but man...that still has me hesitant to buy another Audi.

It's not that it's persistent or not, it's just that it survives combustion. 99% of oil vapours also leave during combustion and ends up in the exhaust pipe, just like 99% of the PEA fuel additive leaves as well. We're just playing with the 1% or whatever is left as "blowby gas". The idea is if you want to give your intake valves a chance that you supplement it with that sort of fuel additive.

It's also why I never ever ever put in any gas other than Shell Premium or Chevron Premium. For me I can't get Chevron, but both fuel brands attach that special nitrogen molecule that helps their fuel additives survive combustion as well. Shell markets it as "Shell Nitro", and with Shell Premium where I live, there's 0 ethanol in it, which helps the engine oil resist fuel dilution which helps it not have as much oil vapour that ends up back through the PCV valve.

Long story short, with DI engines, stick to proven ones like the MB application, stick with Shell Premium or Chevron Techron, and throw a fuel additive like Redline SI1 before every oil change. Don't worry about anything else.

Kelvin Bellrose

That sounds like sound advice. I do try to fill with Shell Nitro every chance I can.

How long before an oil change do you put the SI1 in?

superangrypenguin

For me, when I owned a DI car, I usually put in SI1 in one or two gas tank refills prior to an oil change.

teksurv

Yeah, loved the A4, Audi bought it back, shocker right?. Like you I like Audi, but I haven't bought one since. My 204 was flawless and an absolute tank.

[QUOTE=superangrypenguin;7593587]The latter may, but you are a brave brave man with that 2.0 FSI motor. Not only does it have serious carbon intake valve buildup issues, but the cam follower is a flat tappet design. If that gets punched through, then you'll need a new HPFP. Also, that motor is prone to systemic and repetitive coil pack failure. Don't get me wrong, I loved driving that car, but it was a nightmare to maintain so sold it for the W204 and it was a great decision. I miss that B7 A4, but man...that still has me hesitant to buy another Audi.

superangrypenguin

You know, when I read this post I literally laughed out loud because it hit close to home. There's a million things I look for in a car, and I'm a very particular person, but there's a saying about the devil you know versus the devil you don't. In the case of the W204, it's been a tank, and it just keeps on running and running and running. It's literally the first reason why any of us buy cars in the first place (to get from A->B), and I will say the gamble that the next car will be as reliable as the 204 (despite all of the things I want in the next car being thinks that make me salivate) is one that makes me flip flop on buying another car.

If anything, I might just keep the 204 and buy another car, because I feel like I'm going to have a serious case of "man, I should have never sold that car", if I do trade it in.

The 204 is an attestation that if a carmaker does their homework, it pays off. The 204 remains, to date, the most "driven" car prior to launch by Mercedes Benz. It covered the most miles and spent the most time being tested by the boffins in Stuttgart prior to series production. No other model, since this model, has been tested this much, both from a times, and km perspective.

It shows.

teksurv

The interesting thing is you are contemplating going from a compact, nimble and relatively speaking simplistic car (<-- a good thing in terms of reliability) to one that is very large (even SWB) and tech laden. I've followed most of your posts, you know what you are getting into. I understand what you like about the A8. I'm sure it will be quite nice. The 222 is where I'd be in your criteria, excepting the drive. A 740i is a nice combination of size, power and tech that drives like a boat, but less so than the others (even with the new Audi suspension tech). I'd keep the C300 as it is worth more to you than it will be on trade. My C238 is the best car I have owned, very closely followed by my 204 (C350).

W204Motorsports

I know we had this debate but I just emptied my catch can after 6000km and about 100ml of oil came out. It was definitely not moisture or water but oil. If you plan on keeping the car long term, specially a direct injection, I would do as much as possible to prevent carbon build up, or at least greatly reduce it.

W204Motorsports

Putting cleaners in the gas will do absolutely nothing on DI engines unfortunately since the injectors will never spray the cleaner where the carbon actually builds up. You need to run a cleaner through the intake before oil changes, that will help a lot and actually clean the back of the intake valves.

superangrypenguin

Please re-read what I posted upthread. You are re-repeating a comment that I have already addressed, and your comment is facutally incorrect. This has nothing to do with traditional port fuel injection fuel additives.

There are no cleaners that actually do a decent job with what you are referring to. The BG GDI top cleaner thing did basically nothing for my old DI Audi. Once it forms, if the carbon buildup does not achieve steady state and keeps on building, you're f*****.

I feel like this thread is going to derail itself, but I have wasted 6 years of my life with monthly UOAs, and looked inside using a boroscope of intake valves during that entire time.

The Redline SI1 cleaner almost doubled the amount of mileage it would take for the old Audi (and my old RS4) to require a manual carbon clean. For a decently built DI engine like the MB ones, this issue shouldn't even rear its ugly head, but throw in a bottle of PEA based fuel based cleaner for good measure.

superangrypenguin

Yes, there will be some oil vapour/residue, just like there is some fuel detergent residue for PEA cleaners as they survive combustion and would also be part of the crap that your catch can would collect.

The theory is that all of that crap that would go past the intake valve - the PEA additive would have some effect to keeping the carbon/oil vapour from sticking.

This would only work with engines that have a decent air oil separator in the first place. The old 2.0 FSI engines from Audi were hopeless, as an example, and no matter what you did, catch can or not, your car would slowly die of cancer.

ItalianJoe1

Has not been an issue yet even on the higer mileage engines we pull apart for various reasons. Yes some of the valves don't look clean like a port-injected engine, but MB doesn't have nearly the valve build up problems I've seen with BMW or Chevy engines even.

superangrypenguin

Can you please share at what mileage do you see engines achieving a steady state of carbon buildup?

It's interesting, for me, to see how the air oil separators work for the M276/M278 engines. The 6 cylinder has one air oil separator, and the 8 has two. So that's odd. I wonder if the 6 cylinder gunks up sooner as 1 separator has to service 6 cylinders?

Anyways, sorry. Back to my original question, if I may ask. I'm curious do you notice say a 40,000 mile engine has the same level of carbon as a 120,000 mile engine? Curious when do you see steady state on these engines from an intake valve carbon buildup.

I know CELs, misfires and such as a result of carbon buildup does not occur on MB. It's like the Stuttgart boffins have cured cancer, and good for them.