GM DOD/AFM Interesting Oil Observations

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Here is a later TSB from SILVERADOSIERRA.com:

Oil Consumption

You can download the PDF file for this TSB.

I noticed this message,

Quote:
Attention

This bulletin does not apply to the Buick Rainier, Chevrolet TrailBlazer and GMC Envoy equipped with LH6 due to a different design oil pan and AFM pressure relief valve.

My Trailblazer has the LH6 engine option.
 
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A co-worker of mine had a '07 Silverado with the AFM engine. He kept it through about 70,000 miles and battled oil consumption issues the entire time. He traded it for an F-150.
 
Originally Posted By: MolaKule
Here is a later TSB from SILVERADOSIERRA.com:

Oil Consumption

You can download the PDF file for this TSB.



Yeah, that's one TSB that we perused last year before pulling the trigger on ours.

Basically, any GM NNBS truck built after January 2011 will have the latest AFM configuration, and requires Dexos spec oils for warranty, which should mitigate field oil quality factors.

Earlier engines that have the problem can be updated with the upper and lower end baffling and ultimately pistons/rings. GM reduced/eliminated the earlier consumption test threshold, which was really annoying those affected.

How effective the fixes are after the problem starts seems to vary. But most report the consumption resolved after repairs. I would probably err towards running Dexos compliant oils in the earlier ones as well, fixed or not.

Our '11 was very late production. As mentioned above, we've had no consumption issues. Now running a Range AFM disabler, I suspect we never will.

I frankly think AFM a useless nuisance on the 1/2 ton trucks and should be deleted. The fuel savings just aren't meaningful for most.
 
Originally Posted By: tony1679
I have no idea if GM has improved the technology over the years.

The tsb confirms this. Saying I'm wrong and then comparing a model 3-5 years newer to prove it is idiotic.

Also regarding afm, what most do not know is that there are other side effects GM has cleverly covered up.


Bottom line - everyone is entitled to their own opinion. Mine has been stated. But opinions are irrelevant. I presented facts. These are my "test results." And I am completely satisfied with them.


All you have presented is typical Internet hyperbole. The vast numbers of V8 engines out there with "GM" on them is a real "fact" not based on your cockamamie conclusions. Most run just fine, and are not squealing loudly about AFM problems.

I wonder how many other folks realize what a TSB really means...
 
Originally Posted By: SteveSRT8


I wonder how many other folks realize what a TSB really means...


Technical Service Bulletin. Not a recall, not always an acknowledgment of any problem, and not necessarily a directive for any required service.

They are merely recommended/approved procedures for identifying and/or addressing issues that the manufacturer acknowledges to exist.

In this instance, there was enough of an issue for GM to formulate a diagnostic and repair procedure. This TSB speaks for itself. More than a TSB on how to clean wiper blades, but not a recall-level procedure by any means.

I have no doubt that some earlier owners had AFM consumption problems, or GM, notorious for bean counting, would not have gone to the trouble and expense of designing updated service parts.
 
Originally Posted By: SteveSRT8

All you have presented is typical Internet hyperbole. The vast numbers of V8 engines out there with "GM" on them is a real "fact" not based on your cockamamie conclusions. Most run just fine, and are not squealing loudly about AFM problems.

I wonder how many other folks realize what a TSB really means...


Wow. Ok. Obviously I have to simplify this for you.

I agree most don't have this problem. The definition of most is > 50%. I am willing to bet that there are at least some vehicles within the majority that actually do have problems, but the owners are oblivious. But you will probably say I am wrong about that too. So I will move on.

You want facts. So here they are:

FACT: My vehicle had excessive oil consumption.

FACT: GM has a TSB for oil consumption. Regardless of how you define TSB.

FACT: Disabling AFM on my vehicle eliminated the oil consumption problem. That means ZERO oil loss. There were no other variables.

FACT: My problem is solved.

I wonder how many other folks realize what a fact really is...
 
Originally Posted By: Volvohead
Originally Posted By: SteveSRT8


I wonder how many other folks realize what a TSB really means...


Technical Service Bulletin. Not a recall, not always an acknowledgment of any problem, and not necessarily a directive for any required service.

They are merely recommended/approved procedures for identifying and/or addressing issues that the manufacturer acknowledges to exist.

In this instance, there was enough of an issue for GM to formulate a diagnostic and repair procedure. This TSB speaks for itself. More than a TSB on how to clean wiper blades, but not a recall-level procedure by any means.

I have no doubt that some earlier owners had AFM consumption problems, or GM, notorious for bean counting, would not have gone to the trouble and expense of designing updated service parts.


The facts are that TSB's don't necessarily mean much at all. Simply that if your particular vehicle exhibits the listed issues then they are authorized to repair it.

I have examples of TSB's where NOTHING needs to be done, only that the mfgr is authorizing repairs if the customer demonstrates the need.

Obviously the OP's vehicle demonstrates the need for them, and dealers these days won't touch you with a ten foot pole unless they can bill someone for the repairs. Hence a TSB is issued in an attempt to resolve it.

But loudly squealing about so-called "facts" while simultaneously spouting guesses about numbers of involved vehicles is far from the type of info this site usually insists on.

I will repeat that GM makes well over one million V8's every year. This is a real fact, and if even one percent of them were bad that's 100k units out there. Think about that a minute and the economic realities start to come into the picture. If even 20% of the total production was involved it would be another bankruptcy for GM.

The total number of vehicles with this issue must be very small, as we buy GM trucks on a regular basis here. ALL ARE V8 powered! NONE USE OIL! How can that be?

And continuously calling people idiots and implying they are simple while ranting does nothing for me, maybe others here enjoy it...
 
Steve - you are clearly lost.

We know what a tsb is. There is no need to clarify it for us.

The facts stated are plain, simple facts. Typed in clear English. Yes, I guessed on some information. But I never said any of those guesses were correct or factual. The "facts" were entirely separate.

Here is a fact: 1% of one million = Ten thousand. Not 100k.

Wherever you buy GM trucks on a regular basis, you are probably talking about 2011+ trucks. Those supposedly don't use oil. Therefore I believe you.

Nobody was called an idiot. And if anybody implied that anyone is "simple" it was you with your post from yesterday.

Nobody was squealing. But most people do love bacon.
 
Originally Posted By: tony1679
The tsb confirms this. Saying I'm wrong and then comparing a model 3-5 years newer to prove it is idiotic. So is comparing at 33k mile car to a 100k mile car.



Ooops. Sorry about the decimal point error. Obviously you forgot your own words.

Psst, we have been buying GM trucks for DECADES, you know very little about us, so confine the conjecture to the subject at hand, eh?
 
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Originally Posted By: SteveSRT8
Ooops. Sorry about the decimal point error. Obviously you forgot your own words.

Psst, we have been buying GM trucks for DECADES, you know very little about us, so confine the conjecture to the subject at hand, eh?


Yes. A TSB confirms a problem. It does not mean everyone, or even a majority has a problem. It means some.

I don't know a single thing about you. You're name is probably Steve and you own or have a love for an SRT8. That's what I THINK I know. Nothing more.

But what I do know is we are comparing two different vehicles. Mine is transversely mounted with many differences compared to 5.3 trucks. The crankshaft being one of many. Apples and oranges.

AFM is NOT limited to just V8 engines. The 3.9 in the 2008 LTZ Impala is one example.

I am not assuming to know anything about your vehicles. Perhaps you should not assume anything about mine...
 
Originally Posted By: 440Magnum

Originally Posted By: HangFire
Originally Posted By: lexus114
that afm stuff didnt work in the 80s either. so why would they even consider it now? that is a bad idea no matter how much electronics have improved.


Cylinder deactivation can, and does, work great... if the valves are floated. If they continue moving in 4-stroke configuration, you get suction on (what would be) the power stroke and thus oil consumption.


Keeping the valves moving doesn't even save fuel, because you're dragging dead cylinders along with huge pumping losses.


OK, and those "dead cylinders" aren't "dragging" anyway? And, compressing and uncompressing cylinder air doesn't have "huge pumping losses," and sucking oil into the cylinder is great, but carefully timed minor valve openings that avoid both issues and supplement or replace EGR and can improve the performance of the other cylinders through improved manifold flow, that's bad???

I was saying the way that GM is doing it is the wrong approach. I think the entire contents of this thread backs that up. There are other ways to do this. Some require serious fluid dynamics modeling, which is one of those self-investment issues. Better to just blindly throw some mechanical technology at it and hope it all works out.
 
Originally Posted By: HangFire
Originally Posted By: 440Magnum

Originally Posted By: HangFire
Originally Posted By: lexus114
that afm stuff didnt work in the 80s either. so why would they even consider it now? that is a bad idea no matter how much electronics have improved.


Cylinder deactivation can, and does, work great... if the valves are floated. If they continue moving in 4-stroke configuration, you get suction on (what would be) the power stroke and thus oil consumption.


Keeping the valves moving doesn't even save fuel, because you're dragging dead cylinders along with huge pumping losses.


OK, and those "dead cylinders" aren't "dragging" anyway? And, compressing and uncompressing cylinder air doesn't have "huge pumping losses," and sucking oil into the cylinder is great, but carefully timed minor valve openings that avoid both issues and supplement or replace EGR and can improve the performance of the other cylinders through improved manifold flow, that's bad???

I was saying the way that GM is doing it is the wrong approach. I think the entire contents of this thread backs that up. There are other ways to do this. Some require serious fluid dynamics modeling, which is one of those self-investment issues. Better to just blindly throw some mechanical technology at it and hope it all works out.


No. Compressing and uncompressing cylinder gas doesn't have huge pumping losses. With the valves closed, the trapped gas in the cylinder acts as a spring, so the energy required to compress it is recovered as it is uncompressed. As a matter of fact, there are no pumping losses because no gases are being pumped into or out of the cylinders.

The key to oil control in the deactivated cylinders is to deactivate the valves after the intake valve has closed so that a fresh charge is trapped and burnt and kept in the cylinder because the exhaust valve does not open. This assures that the cylinder pressure remains above crankcase pressure so that oil cannot be sucked up past the rings. The practical problem then is that ring end gaps allow the trapped charge to leak into the crankcase through successive engine revolutions. The deactivated cylinders must be reactivated periodically to refresh the trapped charge.

You are right that the deactivated cylinders still contribute to engine friction, but the net effect of cylinder deactivation is improved BSFC when running on 4 cylinders compared to running the same power setting on 8.
 
Originally Posted By: SteveSRT8
Originally Posted By: Volvohead
Originally Posted By: SteveSRT8


I wonder how many other folks realize what a TSB really means...


Technical Service Bulletin. . . .


And continuously calling people idiots and implying they are simple while ranting does nothing for me, maybe others here enjoy it...


When have I ever called anyone here an idiot? If you think that was implying simplicity or ranting, I think you have a real issue.

I'm going to assume your response was intended for someone else.
 
Originally Posted By: Volvohead
When have I ever called anyone here an idiot? If you think that was implying simplicity or ranting, I think you have a real issue.

I'm going to assume your response was intended for someone else.


I think that was meant for me, but I don't get it either... He came out of nowhere with that one.
 
Originally Posted By: tony1679
Saying I'm wrong and then comparing a model 3-5 years newer to prove it is idiotic. So is comparing at 33k mile car to a 100k mile car.


With apologies to Volvohead.

Tony, is that you or not?
 
Yes that was me. This was regarding Harry46 (2010+ vehicles) and Durango (33k miles). I was calling the comparisons idiotic. Not the people involved. If I offended either of them, I apologize. But how does this relate to you?

I'm not trying to instigate or attack you, I'm just trying to find an end to this argument. It's completely derailing this thread.
 
I'm a bit of an "ecomodder." Here is my issue with cylinder deactivation. It takes X amount of power to move the vehicle at highway speed, 8cyl, 6cyl, 4cyl, does not matter. They should be cutting these things downs to 4cyl when sitting at red lights to save fuel and using aggressive DFCO settings.

I drive a new GLK350 frequently, it shuts off after a couple seconds stopped. Sitting in Manhattan traffic leaving midtown then getting on the Jersey turnpike doing 80 all the way to Berwyn PA I average 26mpg. When I hit the turnpike my MPG is 18, without the eco mode it would probably be 9.

I can average 30 mpg on the highway with the CTS-V but I have a lean cruise built into my tune and very aggressive DFCO settings (doesn't turn the injectors back on until 1050 rpms when you let off the gas pedal)
 
Often, the reality is between the extremes.

Can we just agree that there were some people having problems with the early AFM engines, but not so many as to constitute a major issue?

Besides, to the extent some people were having a problem, it has, for the most part, been addressed by GM with production revisions. The incidence of internet complaints about AFM has dramatically fallen off since '10.
 
Originally Posted By: Shark

I can average 30 mpg on the highway with the CTS-V but I have a lean cruise built into my tune and very aggressive DFCO settings (doesn't turn the injectors back on until 1050 rpms when you let off the gas pedal)


My but those "antiquated" pushrod V8's are surprisingly efficient! Who else has a 400-HP car that gets 30 mpg on the highway?

How lean is your lean cruise? Do you have wideband O2 sensors on it?
 
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