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Another Quart of Oil Requested - 2005 Mercedes-Benz CL65 AMG Long-Term Road Test
Edmunds.com
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Another Quart of Oil Requested - 2005 Mercedes-Benz CL65 AMG Long-Term Road Test
Edmunds.com conducts a long-term test of the 2005 Mercedes-Benz CL65 AMG and finds that its rate of oil consumption is high, but apparently not atypical.
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looks like its starting to get a LITTLE better after you had all that work done on it guess wait and see
My BMW M3 (e36) used to burn oil, though only at half or one-third the rate you're seeing. I'd add a quart every 3-4k miles. Maybe you burn twice as fast because V12 = 2 * I6 ?
Jason- beyond compression seal of the rings, another reason is the PCV system. If oil separation is poorly designed, the engine can and will eat oil, particularly because of how many cylinders and how much displacement this engine has... the blowby level is guaranteed to be enormous. Pull off the intake manifold and check for oil stains.
You could, to enlighten us all, drop a line to AMG and try using your credentials as a journalist to get in touch with an engineer:
marketing-amg@daimler.com or +49 7144 302 0. That's a call to Affalterbach, Germany; just so you know what you're getting into.
Also, there's a Mercedes museum and regional office in Irvine, CA. You could call or visit.
If all else fails, email Mercedes-Benz through their customer support on mbusa.com, or call them at 1-800-367-6372.
I have to believe that as an automotive publication, Edmunds has more regular ways to contact companies about their products, so ask around in the office.
I look forward to seeing another blog post from you expounding on why these engines burn so much oil!
It could be sucked up by the turbos. Next time you start 'er up cold, have someone standing by the tail pipe looking for a wisp of blue smoke--just a few seconds worth.
If that doesn't show up, then this rate of consumption is a bit alarming. I'd have a cylinder leakdown test performed. If that engine blows up, you are staring a monstrous repair bill in the face. one that will approach the entire value of the car.
If the leakdown test shows only upper cylinder wear (valve stem seals/guides) you might justify a repair; but if it shows bottom end wear I'd ditch that puppy like it was a hand grenade with a wobbly pin.
I don't think an engine burning oil is normal any more. At one time when tolerances in the engine were not as tight as they are now, yes. Not any more. I have owned a Mazda, Nissan, 2 Hondas and an Acura and none of them burned any oil between changes. The Acura always goes 10,000 miles between changes and the level of 0W20 on the dipstick remains the same.
Did any one think that maybe the oil level sensor is malfunctioning and giving a false low oil warning? I would drain and measure the amount of oil to check the accuracy of the sensors.
Some oil burning is okay--a small amount of oil thrown into the combustion chamber might actually do some good. But we are talking teaspoons, not quarts.
@allthingshonda, ask anyone you know with Nissans VQ v6 if oil burning is still normal. And as manufacturers continue to scramble for each fraction of a MPG point, "low friction" engine designs are letting more and more blowby past the rings.
As for Edmunds' CL65, most 275s drink oil because of poor break-in of the Silitec cylinder liners. Thats compounded by a PCV system thats open to full boost at WOT.
@mieden I don't have to ask anyone with a Nissan VQ, I owned one for 5 years. The 3.5 VQ V6 never burned oil. I refuse to believe I'm just that lucky getting cars that don't burn oil. My Dad has a Ford Ranger with 200,000 miles on it and it doesn't burn any oil. Leaks oil yes, but doesn't burn oil.
PCV systems should be designed to be closed under full boost at WOT (or at least that's current design "best practice")... even if it isn't, doesn't this engine have oil separation baffles built in? Seems like a pretty big oversight if not.
They have added 5 quarts in less than 6k miles. Where is it going?
I would assume that the Skyactiv engine in my Mazda3 is pretty low friction, and it uses very thin oil (0W20), and there is no measurable oil consumption.
@allthingshonda, I had the opposite experience with an M35 and know many others who have too. But that was just an example, my point was that its not near as common as it once was, but there are still oil burners out there. BMWs N63 V8 is a big drinker too.
@duck87, it uses a "centrifugal oil-air separator" that runs off the front of the camshaft since these dont have vvt. It spins the oil from the vapors in its little centrifuge and dumps the "oil free" vapors into the intake at part load, and straight into the left turbo intake at full load. Like any PCV system, with age and deferred maintenance, they become less and less efficient at separating the oil and it ends up getting routed with the rest of the vapors.
Some of the best racing engines in the world burn oil. Burning oil is not a defect per se--it can be a characteristic that will never change during the engine's life, OR it can be an indication of trouble. It all depends on how it continues to progress over time.
it was due to either PCV or EGR but in the bad good old days, pontiac sent a specific letter about oil consumption due to oil getting ingested by the intake during engine-braking >3000 rpm . i don't do much high-rpm engine-braking with my LS2 car, but occasionally yes... it's never required much oil so far, maybe half-quart in 10k miles. 112k miles and counting.
If this were happening in an American made car, it would be considered a piece of junk! Any oil burning/consumption of oil in modern cars in unacceptable.
Oh, a little oil consumption is fine, and actually probably good for the car. It's nothing to worry about. Some of the most expensive and exotic cars in the world will do this. I would tolerate...oh, maybe 1/2 quart between changes, that's about it, on a new car with 7K-10K intervals.
The centrifugal camshaft separator isn't really that effective at separating fine oil mist. That's part of the reason why Mercedes went to a big stonkin' oil separator in the valley of their turbo V6 engines while retaining the centrifugal oil separator as a "big particle pre-separator". Actually performance with this separator should not degrade over time since it's a big chunk of plastic, unless it has been fouled up. More likely, as engine blowby increases as the engine ages, oil consumption will increase. The PCV valve itself is probably also to blame.
I cannot imagine Mercedes simply utilizing the centrifugal separator on such a large AND turbocharged engine, as it's better suited to smaller naturally aspirated engines if used by itself. This could definitely be a reason why the engine is eating oil.
My 1999 Acura TL with 257,000+ miles on the clock burns absolutely zero oil.
@duck87, the "performance degradation over time" IS the fouling of the separator. I have never seen a centrifugal or vortex separator with 50K or more on it that wasn't beginning to foul, or was already fouled enough to cause a driveability issue, however slight. With today's extended service intervals, one or two late oil changes is all it really takes. You seem very well informed on PCV design, like it may be related to your occupation. Do you have any insight on why most of these systems aren't designed better? Every intake i pull is usually saturated in PCV gunk. Direct injected engines being the worst, as there's no fuel wash over the intake valves to keep them clean.
There are quite a few different oil separator designs, from a simple mesh trap, to a tube with tiny holes, or to the centrifugal type. I guess if the PCV isn't working, then that builds up crankcase pressures and might cause more oil consumption.
So on an older engine, everything is under suspicion, from the oil separator to the PCV to actual engine wear.
With newer cars, I'd guess you'd always want to look at the oil separator and PCV first.
You would need to ask these companies why their designs aren't up to snuff, but my immediate suspicion is that they got ahead of themselves on the technology front (DI, turbocharging) and never properly compensated for PCV systems that do a good job separating oil from blowby... nor did they really develop their engines with attention to keeping the engine oil 'happy'. These two things combined seem to kill engines quicker than anything else (other than bad sealing and coolant loops). It seems, for example, that Audi didn't think about the implications of intake valve coking when they started using DI, and their PCV systems were archaic at the time. Also, for some reason the higher performance German engines always require some sort of specialized oil (implying that they have specially demanding requirements, probably temps and oil breakdown to prevent sludging), so I would think there's some level of compensating going on for engine design.
But I would note that Mercedes is pretty unique in the industry for using this camshaft-style centrifugal separator-everyone else and their grandma uses some sort of baffle system in the valve covers. Why is that? I'm genuinely curious.
I would also note that there ARE automakers that do a pretty good job with their systems. I know people are going to hate this when I say it, but the Japanese do a pretty good job- they were late to the party with direct injection, but their PCV systems are well designed to compensate... and I have never really seen coking with those systems. Actually, for most (newer) American designs I haven't seen it either.
Well, if the PCV valve ain't working, all that pressure is probably blowing out the other tubes in the PCV system, which does cause more oil consumption. However, if the entire PCV system is blocked and crankcase pressure builds, you have serious issues...
Anyone know if the "regular" 2003-2006 (and pretty sure it continued unchanged 2007+ as well) twin turbo V12 has the same oilconsumption level or oil separator system?