Yes. 90% of engine wear occurs within the first 30 seconds of engine startup, and because a 0W40 is thinner when cold than a 5W40, it gets to critical engine bits (like your valve lifters / tappets) and starts to lubricate them that much quicker. Now, metals expand when hot, so on a cold engine where the space between your piston rings and cylinder walls is going to be the largest, much more of the thinner oil will get past which you end up burning off. You'll burn about three times as much oil with 0W40 than a 5W40, but all of it occurs when the engine is cold. If you take two identical engines and fill one up with 0W40 and the other with 5W40 oil, start them once and then drive both for 5000 miles without ever shutting them off, the oil level between the two is going to be the same because once the engines warm up both oils are going to be equally viscous and you'll thus burn off equal amounts of each.

 

Im bumping this thread because I've continued to monitor it after taking to an indy with no indications of a problem. Here are my takeaways:

Car seems to burn around a liter 800-1000 miles depending on driving characteristics so Diabolis' post (#9) seems to fall in line with that, although, I still feel like that is a bit excessive...

Another worry is the amount of smoke I see during startup. Every once in a while, a big cloud of smoke with pour out but that will be the end of it. I've had someone video record me under heavy throttle and downhill coasts and nothing more than your normal black smoke from un-burnt fuel. I will be taking it to the dealer next week to get another opinion.

Besides compression/leakdown and engine tear down, what are some other troubleshooting methods? Diabolis' suggestion of scoping seems to be the only thing.

The car feels strong and the dyno numbers show absolutely no loss in power so I'm stumped and either reading too much into this or have a serious problem that seems to be hiding from any true symptoms besides oil consumption.

 

I wouldn't worry about it, these engines eat a lot of oil. Mine does the same thing.

 

I also agree. That amount of oil consumption is not a big deal.

I would not let anyone tear into my motor over that.

 

Cornerjunkie - depends on the viscosity of oil used. If you're running 0W-40, that is perfectly normal for a healthy M156 engine. If it's a 5W-40 sythetic, it does appear a little excessive. Not too severe, but enough that it warrants caution and IMHO further investigation if you want to keep the car for a few years. Repalcement M156 engines from MB are about $85K new and about $35K rebuilt, so you ought to weigh the cost of the inspection vs. the potential of looking at a repair bill that's higher than what the car is worth. Been there myself (not with a MB) and it is an *extremely* unpleasant feeling, so I would err on the side of caution.

A visual cylinder inspection with a borescope when the pistons are at BDC would show any scoring that may start well below TDC where the compression / leakdown is measured. It's the only other "non-destructive" test where they don't need to tear into the engine.

 

Wow- more than a new w204 C63 new.

 

Thanks - Taking it to a dealership next week for another diagnostic. I am going to specifically request a compression/leakdown test again along with a borescope. I am using 0W-40 so I guess it is in line with what is being said.

Is the smoke during startup strictly a nature of the beast with these motors? I understand they have loose tolerances so oil is bound to get through, but could it be valve seals? Maybe I should remove the intake manifold to see how much oil is visible to see if that could be the cause...

 

How are your plugs looking?

 

I have no smoke on start up.


That would indicate leaky valve stem seals. Oil collects on the valve and is burned off when it opens and fires up.

 

Are you sure it´s not watervapor-smoke at start up? All cars have it and it´s normal!
It´s white and can be very noticable during colder weatherconditions.

 

Its smoke. It's not a consistent vapor like you see with condensation. What I'm taking about is a "puff" at initial ignition startup then nothing.

 

That's what I'm starting to think.

 

I second Merc63's suggestion that it looks like leaky valve stem seals - they become hard and brittle over time - if you get a blue-ish puff of smoke at startup but it doesn't smoke all the time.

 

I thought this was brought up at AMG PL. Was this not one of the reason they say to use 5w40 instead of 0w40? Not sure though,

 

NO ONE in any official capacity has ever suggested using 5W-40 instead of 0W-40 on the AMG PL. I have yet to see a single post by anyone from AMG or MB where they recommend the use of 5W-40 over 0W-40.

And, IIRC the 5W-40 vs. 0W-40 debate was in regard to the thinner oil's tendency to drain easier from the flat tappets after the engine is shut off, however, this is debatable at best as what most people fail to realize is that the oil thickness when the oil is cold is about six times that when it is hot, so 99.9% of the drain occurs in the first 30 minutes after you shut off the motor - when BOTH the 0W-40 and the 5W-40 oils are equally thick (or, rather thin) as opposed to the time after the engine completely cools off. Furthermore, seeing as 90% of engine wear occurs in the first 30 seconds after a cold start, the thinner oil flows easier when cold and starts to lubricate those same tappets that much faster than a thicker one, so all other things being equal it is actually better for your engine.

While a thicker oil will mask the sympoms of valve train wear whether it's cams, lifters / tappets or valve stem seals since it doesn't flow as easily so you burn less of it, nothign except replacing the worn cams, tappets or stem seals will actually fix the problem. Period.

 

This is where I remember that info abow 5w40 from:
https://mbworld.org/forums/w211-amg/...g-pl-info.html

I do have a question. So the 5w40 and 0w40 are the same "thinness" at operating temp. At cold startup the 5w40 is thicker than the 0w40 but both are still thicker than at operating temp. When and why does the 0w40 have more oil consumption? I thought it was during startup, but 0w40 is thicker at startup than 5w40 is at operating temp. Does this have something to do with clearances of cold engines?

 

Ahhh... that post. I have already extensively elaborated on it in an earler thread, but my key point and where the fun started (and things went downhill) was in post #72 at https://mbworld.org/forums/c63-amg-w...ml#post6229169 (read the entire tread if you have the time). It has nothing to do with it being better for the engine - it's about environmental friendliness when the 6.2L M156 was the most powerful and largest capacity AMG engine and MB had to meet tighter emission standards.

As for the second part of your question, you're spot-on about the piston-to-cylinder clearance on a cold engine and when the burn-off occurs. See my posts at https://mbworld.org/forums/c63-amg-w...ml#post6334736 and https://mbworld.org/forums/c63-amg-w...ml#post6424692.

 

I recall at least a couple prior discussions about a thin black cloud at startup. My recollection is that most instances were reported on the first start-up after the car had been run very briefly and then shut down before anything had a chance to warm up.

I've had this happen a couple times. I had scratched oil off my probable-cause list because it is so much more viscous when cold, and because the cloud never appeared after a warm-engine shutdown. I had assumed that the cloud was unburned fuel from the earlier cold start.

 

The black puffs are from unburnt fuel as the M156 motor very definitely starts on the rich side on purpose when cold (that's what gives it that wonderful bark for the first few seconds when you fire it up) and IIRC continues to squrt in small amounts of fuel even during the exhaust cycle with the valves partially open in order to get the pre-cats up to temperature as quckly as possible. You're 100% correct in that the black puff is fuel and not oil.

P.S. That doesn't change the fact that most of the oil being burned off in an otherwise healthy engine is also when the motor is cold - but the puff you see is from the fuel, not oil. Smoke from burning oil is blueish in colour (and coolant usually white).

 

Thats fairly long. So a question without really reading all of it. From my BMW M3 days when the factory fill was 5w-40 and I filled with M1 0w-40. Fist thing I noticed was that the 0w40 was leaking out of the top of the oil filter canister, right past the rubber gaskets. Weird, I don't really when it happens, hot or cold, but it does happen. Anyway, back then the M3 consumed much more (about 4x) oil than at 5w40. My current thought was that burning all that oil (0w40) with an ash content of 1.3 in the M156 will leave more deposits inside the combustion chamber or cats than the 5w40 with an ash content of .9. Every 5000 miles I burn about 1 quart of 5w40 or 4 quarts of 0w40. So if I multiply those (for ratio purposes only) , for every 5000 miles 5w40 puts in about .9 of ash and 0w40 puts in (1.3x4=5.2) of ash. Thats a large difference. Of course both could be small enough to not really affect anything, much like eating a teaspoon of ice cream or a tablespoon. Either way it wont affect my weight.

The second issue then is the TBN on the 5w40 is much lower than the 0w40, but that can be remedied by more freq oil change, which just cost more time and money

 

Sure, in a worn engine where a lot of oil gets in the combustion chamber (either becuase of worn piston rings, cylinder scoring or through worn valve guides), oils with a high ash content - like HDEOs for commercial diesel applications for example - can create deposits on the rings, plugs and valves. However, you ought to keep things in perspective here. A low ash oil leaves less ash residue, but you need the ash to suspend the soot and control the oil acidity and moisture content. Because low ash oils have a low TBN, they don't allow for longer drain intervals. And, since your M156 engine runs on gasoline and there is a LOT of sulfur in the garbage that passes as gasoline here in North America, your engine requires an oil with a higher TBN if you're only going to change the oil once a year, and consequently higher ash content unless you're prepared to change the oil it every 3,000 km.


Second, the ash essentially acts as a detergent, so a higher ash content really means higher detergent content. And, last but certainly not least, the ash actually comes from the anti-wear and anti-oxidant additives like ZDDP and Moly. A high-performance, high output engine like the M156 where you have high-load elements in the valvetrain and pistons/rods/crank/bearings necessitates an oil with lots of anti-wear additives.


The problem with additive chemistry is that those same additives preclude the use of friction modifiers which improve fuel economy, so the high SAPS / ZDDP oils are not as fuel efficient. Furthermore, the phosphorus in the ZDDP is bad for your catalytic converter (it's what shortens their life span), and furthermore, the ash also clogs up the DPFs on the newer diesels with their expensive exhaust aftertreatment systems, which BTW is why all the new diesels require Ultra Low Sulphur Diesel. The irony is that the refieries are now forced to make ULSD, but the sulphur content in gasoline is higher than ever as essentially they have all completely retooled their production to produce the cheapest and dirtiest gas they can get away with, and rely on the mandated Ethanol content in the US to bring up the octane rating of the gas to what you see on the pump.


So - there you have it. You can either have your MB 229.5-spec Mobil 1 0W-40 with its high ZDDP, Moly and SAPS additives that is thin when cold, provides less engine wear, can neutralize a fair bit of acid so you can safely change it only once a year but will clog up your cats sooner and isn't as fuel-efficient, or you can use a MB 229.51-spec low ZDDP and low-SAPS oil that will give you better fuel economy, is better for the environment and will prolong the life of your catalytic converters at the cost of placing more wear on your M156 engine. The choice between the two is entirely yours.

 

I assume even on a good engine, if the amount of oil consumption is three times as much with the 0w40, all that oil was getting dumped into the cylinders during cold start running when the engine clearances will allow it. That would be my worry, burning all that oil in the cylinders and causing deposits.

The M1 Formula M 5w40 (not ESP) has low ash (0.9) , lower than some of the standard retail available ESP but the TBN is also low at 8. I assume here that 10 quarts would be sufficient to last maybe the whole year or 10 thousand miles, if not one would change at 6 months or 5000 miles.

 

Is the TBN test worth doing as an aid to help decide when to change oil?

 

I suppose you can initially use it to establish your cars particular oil change interval.

 

1 - Not necessarily. Gasoline - seeing as most stuff we get is already crap so they add more of the additives at the fuel depot these days, and furthermore, has Ethanol which is has a tendency to dissove anything - has plenty of detergent additives itself, so whatever miniscule amount of ash is present in the oil you burn at startup gets washed away before it has a chance to start forming deposit formations. I've never seen ash buildup residue on a gasoline engine. The examples I mentioned earler are from heavy-duty diesel engines used in large trucks and excavators that are in use 23 hours a day in a mine - the diesel doesn't have the detergent levels that gasoline does nor the Ethanol. I don't know what you have in the US, but two tanks of Shell V-Power for example (the "Nitrogen-Enriched" stuff or whatever they call it) will clean fuel injectors and valves as good as a can of fuel cleaner that you directly injected in the fuel rail would have ten years ago. I guess what I am saying is that the ash deposits from burning high-SAPS oil in an otherwise healthy, gasoline-powered engine would be about as detrimental as, say, you visiting a bar where smoking is still allowed for 10 minutes every three months vs. working as a coal miner in the old days for 35 years. You have to keep things in perspective - and besides, in this particular case, spending those 10 minutes in the smoker's bar would have been for you to get your vaccine against Ebola while living in a town where every other person has the virus.


2 - AFAIK the M1 Formula M 5W-40 hasn't been made for quite some time, but it would be a 'high' mid-SAPS oil (0.9% vs. 1.3%), and as you pointed out, has a lower TBN - in addition to having a lower HTHS and being more dense when cold. Again, you ought to look at things in perspectiuve. The M156 had two potential issues that needed attention - one were the headbolts on the early models, and the other the valvetrain wear at startup because of the flat tappet design. While you couldn't do anything at the consumer level about the first issue, if you have an oil that can get to those vulnerable tappets and cams 50% faster than another, which would you choose? Or if you'd like another analogy, you don't worry about the little 1" hermit crab probing at your left little toe when there's a 20' great white shark coming at you with the intention of having breakfast. The litte hermit crab is the potential ash deposit, the great white is engine wear. Again, if you're interested, I did compare the Formula M 5W-40 to the 0W-40 somewhere on this forum, but I'm not going to look for it as it's a moot point at best. It's no longer made or sold.


One of the best, unbiased articles ever written on valvetrain wear and the role of ZDDP and P additives in oil specifically in flat-tappet engines is at http://www.corvetteactioncenter.com/tech/oil/. It's six pages but it is excellent reading material in plain English. The only thing you have to keep in mind is that it was written in 2009 and the specific oils mentioned are for Corvette engines, and that since then the M1 0W-40 (specifically the 0W-40, not all M1 oils) has been redesigned and gone back to being a pure synthetic (Group 4 and 5 base stock) oil and has the right viscosity for the M156 in the C63. And, while in my track P-car I now run Shell Rotella T6 (there was significant cam lobe wear even with M1 15W-50), in the C63 I'd take the M1 0W-40 over anythign else that is present on the market today. 'Nuff said.


Where things are going now is in (1) the design of base stocks that have excellent anti-wear properties and thus have low ZDDP and Moly levels (so low-SAPS) yet meet the highest anti-wear spec in the industry today (VW 504.00/507.00 - see http://lubrizol.com/apps/relperftool/pc.html if you're interested how the different standars compare to one another); Mobil 1 ESP 5W-30 is an example, and (2) the development of ashless P- and PS-based additives as well as advanced zero-SAPS additives like Uniquema's Emkarate DE10479 (again , you can google "Emkarate DE10479" and you'll find some interesting reading if you're so inclined).


Anyway - this kind of discussion really belongs on BITOG, not here. That'a great resource for what's what when it comes to oils.