Yep, Toyota uses both Port Injection & DI to combat carbon build up. MB uses careful design of the DI port shape, port location, and multi-sparks per cycle ensure complete fuel burns, which in turn keeps build up to minimum and maximize efficiency.

 

Another crucial thing is decent fuel, never use less than 91RON. In addition top tier gas contains additional additives to ensure clean combustion. Paradoxically, ethanol which is otherwise detestable because it's hygroscopic has a very high octane rating which leads to very predictable detonation (no more than 10%). As is recommended in the manual, if you ever run fuel of less than 91 octane, make sure you fill your tank with premium at the earliest possible opportunity.

 

Here is a good link regarding top tier gas.
http://consumerreports.org/car-maint...h-extra-price/

 

My SA was adamant about using high quality fuel. Interestingly, he knocked Costco gas even though Costco is a member of the Top Tier gas.

 

It's important to use top tier gasoline, but again the idea that it will prevent carbon build-up is flawed. The consumer reports article showing the valve pictures is from port injection. The only way gasoline would come in contact with the valves in the DI Benz engines is blow-by, and the MSI (multi-spark injection) apparently cuts that possibility out.

Octane rating and whether or not a gasoline is top tier are unrelated.

 

Ditto here my N54 BMW only had Shell gas in it and it had some many DI related problems....

 

Everyone keeps talking about bimmer issues. We are discussing MBs of which no one seems to have problems! The E 300 is far from the first DI engine from MB.

 

I believe that Mercedes first offered DI around 1955 in the 300SL. I've had DI engines from MB and BMW including a 1959 300SL and a 2008 535i both purchased new. I have not had an issue that was DI related except for a BMW recall for the high pressure fuel pump.

 

My point exactly. DI engines have been mainstream for more than a decade. There is no doubt that some early designs, particularly from VW and BMW, did have problems, the estimates Ive read is 4 -10% of the early VW TDI's. But even for those manufacturers those issues are in the past. Modern DI engines are no more prone to intake fouling than any previous technology, particularly when they are run with decent gasoline of the correct octane. Please note, good quality gasoline is not a given in many countries nor necessarily the USA! The fact is that more than 50% of new cars, even cheap ones are now DI. The reasons are obvious, better power and better FE! All diesels are DI plus they use a fuel which is 10's of times more likely to create gunk. You don't see diesel owners running around with their head on fire expecting their engine to self destruct in 50K miles!

 

Interestingly enough I had the chance of seeing a 2015 E class with about 30,000 miles (translated from km for our US friends) in the shop the other day. Intake valves were CAKED in carbon.

It doesn't explain why there wasn't a CEL but they were tearing down the engine for another issue. Wish I had my phone on me for a pic!

 

One should only use Top Tier Gas of the correct octane to avoid such issues.

 

The injector's shape/location and other technical aspects determine the amount of build up. MB's multi-sparks per cycle and injector design have been effective in keeping the carbon build-up to minimal. MB engine did not suffer serious build-up problems as Audi and BMW did. I had a discussion with my MB Service Dept. Foreman and he said carbon build-up not a problem in the current engines.

 

The injector does not prevent it on an DI engine, the injector sprays fuel into the chamber, not down the valves like port fueled engines.

The main thing that saves the MB engines is good PCV control. The engines pull down a ton of vacuum and have good built-in oil separators, so you don't have lots of oil hitting the valves to cause buildup. The higher mileage 276s we see aren't having any significant buildup, but they are all N/A, turbo cars suffer worse normally due to more oil in the system from the charge air system. Even though we don't tear down many 271s, they don't seem affected yet, certainly not like the BMW systems, or the early Chevy Ecotec 4 cyl engines that caked up valves very badly. Both of those were due to poor PCV systems that don't pull the oil out of the charge air.

We do see way more injector failures on the DI cars than you will ever see on a port fueled car, and the injectors are much more expensive. Will be an issue for people out of warranty coverage, as one injector will be in excess of $1000 to replace.

 

So, my 2013 C300 4Matic sport with the M276 engine and at 66k miles (I've owned it since 58k miles) is likely safe from the dreaded carbon build-up sometimes associated with DI engines? I began to use Liquid Moly oil and their fuel additive. As for any other additives, nothing thus far. I use 93 octane at every fill up and when I first bought the car last December, it has run very well with 32 mpg on the open road at 70-75 mph. Performance is great and it starts and runs without hesitation cold or warm. It seems the PCV system is crucial to preventing carbon buildup on the valves and intake runners. It is also apparent that proper, more frequent oil changes with MB spec oil is crucial and necessary. The less oil that is evaporated out of the engine and thru the evaporation PCV system, the less buildup on the valves. It's all about the initial engine design and then proper maintenance with the proper fluids. Being **** with 5k oil changes is also likely necessary. I don't wait for the oil change reminder to come on... I do it every 5k miles and have done so on every car I've owned for the last 50 years.

 

In my previous car, a BMW 535 twin turbo N54 with direct injection, I did oil changes every 5 k with Mobil 1 Synthetic, and later Redline, and always used Shell V-power. Around 80 k miles I had a check engine light, and a scope of the inlet manifold revealed severe coking. I've heard same story for other owners with N54/N55 direct injection engines, and I don't see why Mercedes would be different. This problem only occurs in moderately high milage engines, so you won't see this for a few years. At least for BMW direct injection engines, its unfortunately normal that a walnut blast is a routine service requirement if you keep the car for a while. Using an oil catch after the PCV valve can reduce carbon build up, but installing before 4 years would void probably warranty.

 

Umm guys, fuel that has PEA in it is helpful in preventing carbon buildup in the intake valve, but that's sort of like putting out a forest fire with a garden hose. I mean, it'll do something, but is it super effective? No. Is it better than pissing on the fire with more gasoline? (e.g. using gas from mom and pop's with the bare minimum fuel detergent as per the EPA), absolutely.

Still though I don't see any systemic issue of carbon buildup on MB DI engines which surprises me. That said, I also don't see any systemic issues on the 3.0TFSI engine from Audi, and I have received confirmation that no, we here in N. America do not utilize dual injection as per several Audi World forum sources. DI engines are Audi are just that - DI only, unlike say the Lexus dual injection system.

That said, it seems MB and Audi have fixed their issues.

Pls please please leave the talk about fuel additives from here. It'll make me have even more grey hair. It does not matter that you guys are doing that. Most fuel additives do not even survive combustion, except those with a high amount of PEA, such as Redline SI1 cleaner, but that also causes pretty accelerated breakdown of your engine oil, so best to do an oil change after running that (e.g. it is not something you want to be doing every so often).

Moderation is key, but please, let's leave fuel additives from here...

 

Yes. But this doesn't mean you won't ever have an issue. My 272 engine still uses PFI, and if you take my intake valves versus yours, mine will be pristine, and yours will not be. That said will your buildup cause issues in your day to day driving? Probably not, and while the old Audi FSI 2.0 engines had carbon caked on in 20,000km, yours will probably get that way in say 100,000km. So it's not to say you're free of these issues (just like everyone with DI engines), but it just means you don't have to worry about it until the car is pretty damn old.

That said even I have given up and my next car will have DI.

 

It appears as if the biggest solution to this DI carbon build-up is not what we do as owners (lots of chemical additives and procedures which may/may not work as desired) but is how the manufacturers design their engines to prevent as little evaporation and blow-by through the use of high quality oil to their specs (or exceeding, especially in the NOACK Volatility Test (ASTM D5800)) and using a better design for the PCV and evaporation recovery systems. I would avoid using a catch can since these are not all successful designs and it is difficult to figure out which one actually does trap the evaporated fuel and oil which could have been reused in the engine. In fact, they don't always remove those harmful fluids and gases, allowing some to continue on the path to the valves, resulting in deposits (allegedly less).

While the use of a high-quality fuel will not reduce these deposits on the valves since the fuel is really not injected onto the valves but in the combustion chamber next to the spark plug, our MB engines usually have high compression (the M276 has a 12.5:1 compression) which require higher octane fuels, and the expensive DI injectors need to be kept clean as one can never tell when the fuel, even from a reputable supplier, can be tainted which could begin to clog the injectors. That is why I use an additive, as well as it keeps the fuel lines, fuel pumps and EFI systems cleaner than not using any additive (I use Liqui Moly stuff).

I use the Liqui Moly oil is in the M276, which appears to be an oil which is of a higher quality than Mobil 1, but it's arguable as I've not used it for very long now in both of our cars (1998 SLK 230 Kompressor and the 2013 C300 4Matic sport). I once used Amsoil for a couple of oil changes in our first Benz, a 1986 300SDL, without problems but it was more expensive and harder to find locally, so I went back to Mobil 1 until the first oil change earlier this year on the C300.

At 66k miles, the M276 engine still has strong performance and gets good mileage, especially on the highways.

I will be changing out the spark plugs today and changing the oil tomorrow in the C300 so I will at least be able to see how well the fuel burns and how the oil appears. I may send a sample of oil off to George Murphy or someone who can analyze it. If I do, I'll report the findings.

Also, my 2013 C300 was originally a NY state car, so it has the charcoal filter on the engine side of the intake air filter assembly. I've been contemplating removing it to have freer flowing air at the intake since it seems to restrict a considerable amount of air (guessing about 25% since about that much of the surface area of that filter is solid plastic). Only problem is: to remove it you have to destroy the plastic tabs, negating any replacement of that filter if needed. It is allegedly there for a few states to reduce the amount of gas fumes escaping the engine upon shutdown of the engine. This could also affect the valves since the air is directly being fed to the valves before the injectors in the combustion chamber inject the fuel. So, the air is mixed in the combustion chamber with the fuel and not above the valves before the valves are opened for ignition in the combustion chamber. More air could lead to leaner mixtures, but the ECU will control the flow (at the throttle body) and mixture in the combustion chamber as a direct result of the MAF sensor readings. A freer flowing engine seems to be better than one which restricted, but I am not sure about how this might affect the deposits on the valves and in the intake passages.

 

Interesting, and agreed on all fronts. I have always sent my oil off to Blackstone, and you bring up an interesting point regarding engine oil choices in our engines. I was a bit annoyed yesterday when I read about MB's new 229.6 specification which is namely focused on improving fuel economy, much at the expense of wear protection. It's not right what car manufacturers are doing these days, and direct injected engines have a whole slew of challenges, most among which can be solved by adding a port fuel injector at the cost of, oh, a few hundred dollars/engine? I would certainly pay for it.

I don't have experience with Liquimoly myself, and the only oil I swear by on my PFI engine is the Mobil 1 0W40 product. Would I use it on the M276 once I get it? I'm not so sure as that oil does shear relatively quickly to a low-mid thirties. I used to run German Castrol (0w30 made in Germany) on my 2.0 FSI engine and that actually performed surprisingly well. These low SAP oils though, ugh, they bother me (much for the same reason as 229.6 oils). We're trading fuel economy at the expense of engine longevity, and as someone who loves keeping their cars a while, this pains me.

That said, I have no choice but to jump onto the DI bandwagon now, much to my dismay. MB does seem to be doing a good job though. On my B7A4 with the first DI mass produced engines from Audi, I went through a new PCV valve every oil change (no joke). Even when I sold it back in 2012, I was on the 6th revision that Audi had out, and it still was wrecked every 7500km. If there's one thing I don't see on the MB side of things which has me smiling, is there doesn't seem to be a mass PCV issue, nor does there seem to be rough idle concerns/CELs and the lot which is associated with DI engines.

 

I chose the M276 engine as a stroke of luck. I knew the earlier engines (M272) had balance shafts which seems to me to be an unnecessary item in a V-engine. I can see a balance shaft in a straight 4 cylinder engine as is with the 2.3L 4 in our 1998 SLK. I was surprised to learn the M276 engine was designed with Chrysler (actually, I believe the engine was designed by MB but since Chrysler was a part of Daimler ant the time, Chrysler used it as well so thad to more of a universal design) but all reports of the M276 design are that of it being a solid, well-designed engine. It certainly has the power for one with only 247HP. Makes me wonder how accurate that rating is since the same engine is used in other models with 302HP (with only different ECU tuning?).

In any case, back to the DI subject...the PCV system on this DI engine seems to be working quite well and I look forward to many miles of incident free driving.

 

Thanks! Interestingly enough when I bought my W204, it was the last year the C class offered an engine without DI, and this was post the balance shaft issue, so I bought it right then and there, with a 14% off MSRP to boot

It's been a great workhorse and good to hear about the 276. Done deal, S450 here I come (once they release the vehicle in September!)

 

It looks like you made up your mind. I love the S Class. It's way too big for me or my garage, but I love it just the same. I'm happy you've determined which car best meets your needs. Congratulations!

 

Thank you. I just need the MB gods to release MY19 cars and thus release info on the MY19 discounts. I qualify for close to $12,000 worth of discounts so that helped. If I lived in the United States, there is no way I could have bought the S class, but with my pursuit for the quietest car possible, the E was no longer an option due to the lack of the acoustic comfort package. I would have preferred the E due to the split folding rear seats which I lose in the S, but life's about choices and making the best out of them.

Thanks to people like you for your support in helping me navigate the labyrinth. The other thread involved Audis and after thinking it through, reliability is more important to me than anything. The M276 engine in the S class, being that it's been around a while and the fact that this may be one of the last years of being able to buy a S without the mild hybrid drive system sealed the deal. I love new technology (it pays my bills), but not in cars. Until the order is placed, I will still peruse the E class forums, but now it's a matter of hurrying up and waiting. September can't come soon enough

 

Sounds as if you have a solid car. Mine is as well, I just wish I had been able to avoid a car wash and a parking stop as the lower edge of the front bumper/spoiler is scraped and I have to repair it now. I'm going to use SEM products and fix it myself and use a stone chip flexible paint over the MB OEM brand arctic white paint I found on eBay (2 cans).

Oh, I tried changing plugs today... couldn't get the #6 coil out so I buttoned it back up and will take it into a buddy's shop (whom I have used for years) to put the dang things in. Ugh.

Good luck with the S450... I like the S-class but we no longer need a large car. If I had to buy another Benz at this time, I'd either go back to a W210 E55 or E300TD or maybe an older W126 300SE. Owned both a W126 300SDL and a W210 E300TD at different times, but, alas, both were totaled (no one injured and both were in the city at lower speeds). Loved the W210. It had 180k miles and still had exceptional power and turned over 32mpg on the road. Great car and it was in top condition, which helped with what insurance paid me for it. Loved our 1993 W124 300E 2.8 as well. Great car which is still being driven by a friend's daughter and it now has well over 200k. If I would buy a new Benz, it would be an E-class or maybe a C... not sure. It would have 4Matic, as that is great here in the snow belt (Ohio).

 

The 450 engine in the S Class is pretty much the same engine I have in my E400, with just a few less horses, which is fine given the difference in weight and size. It's a tried and true engine that should serve you well past the time you'll keep the car. Keep us posted on how this continues for you!