GM DOD/AFM Interesting Oil Observations

[MolaKule]

Originally Posted By: tony1679
Originally Posted By: MolaKule
Me too.

We have a 2008 TrailBlazer with the 5.3L V8 and I have used every oil in the industry, including mine (since it is one of my test mules), and have had zilch oil consumption since new.


So are you saying your 5.3 has AFM but is not having issues? Congrats if that is the case. But if you think I'm wrong, you're mistaken. The only variable that changed was the AFM being disabled. Same oil, same filter, same everything.


Tony, I an NOT saying you are wrong nor did I disagree with you.

I am simply recounting my experiences over the last six years and saying my vehicle has the same system and has not used any oil since new.

What I suspect is that possibly the same system is used but the programming is different.

As others have suggested, there is the possibility of other subsystems being affected that is causing your oil consumption.

One quart or more of oil consumption per 1k miles is nuts.

 

[jrustles]

Originally Posted By: tony1679
Originally Posted By: MolaKule
Me too.

We have a 2008 TrailBlazer with the 5.3L V8 and I have used every oil in the industry, including mine (since it is one of my test mules), and have had zilch oil consumption since new.


So are you saying your 5.3 has AFM but is not having issues? Congrats if that is the case. But if you think I'm wrong, you're mistaken. The only variable that changed was the AFM being disabled. Same oil, same filter, same everything.


Glad the tuner worked out for you! I'd disable AFM at the first opportunity too, TBH

There's just something dumb about continuing to pay inertial and friction costs by dragging the rotating/reciprocating assy around as dead weight to save fuel lol. It just seems like such a backwards way to increase efficiency. Sure, one could work three (or four) cylinders closer to their lowest BSFC, and hope that offsets pumping, inertial and friction losses, but it doesn't strike me as a smart thing to do. It also wears half the engine out more than the other half. At 200K miles, what will we have, one bank with more ring wear than the other? larger bearing clearances on one bank vs the other? more piston pin bore wear?

What about the dragging cylinders, did the engineers really think that the same gas pressure would remain sealed in the closed, dead cylinder?? Ya right, more like it'll stabilize at mid stroke, drawing a vaccuum below half stroke and positive pressure above half stroke. Then there is the oil on the cylinder walls not getting scraped off properly due to no gas pressure on the rings, which could foul up the cylinder with oil. Then there are the unpleasant harmonics...
It's just a weird concept to me, for such an idea to make it to market.

 

[tony1679]

Originally Posted By: MolaKule

Tony, I an NOT saying you are wrong nor did I disagree with you.

I am simply recounting my experiences over the last six years and saying my vehicle has the same system and has not used any oil since new.

What I suspect is that possibly the same system is used but the programming is different.

As others have suggested, there is the possibility of other subsystems being affected that is causing your oil consumption.

One quart or more of oil consumption per 1k miles is nuts.


That's what I thought you meant. I was just confused by how it was worded.

And yes, 1+ quart in 1k is nuts. But not according to GM. It's "acceptable" to them. I guess we are the ones who are nuts for bailing them out...

 

[tony1679]

Originally Posted By: jrustles
which could foul up the cylinder with oil...


Yes!!!

I had changed my plugs (iridium) at 80k. I re-checked them at 85k. The full-time cylinders' plugs looked great. The part-time cylinders' plugs (the ones controlled with AFM) were already completely fouled with oil. After 5k. Ridiculous.

 

[sprite1741]

I love my 5.3 with DOD/AFM, as of today I am getting 18.6 mpg in town, haven't been on the highway lately but usually get 28 to 30 mpg on trips to Las Vegas. The speed limit in Idaho is 75 and 80 in Utah. At the most I use 1/3 qt. of oil in 6 mos. The only oil I have used in this engine is Havoline and Chevron conventional and I always use ethanol free premium fuel. No way would I deactivate mine. Have they changed something in the design since 05? Mine is called displacement on demand (DOD), in 06 they changed the name to active fuel management(AFM) but I thought it was name change only.

 

[BrandonT]

I thought the main reason these engines used oil wasn't the cylinder deactivation per se, but the feature (can't remember what) that causes oil vaporization in the oil pan (maybe then making more oil able to make it into the deactivated cylinder)? That said, does anyone know if the 3.6L HFV6 have this oil vaporizing gizmo?

 

[SteveSRT8]

Originally Posted By: tony1679
If by "floated" you mean keeping the valves closed/separated from the rest of the valvetrain, then yes, that is exactly what GM's AFM and Chrysler's MDS does. Still both are plagued with TSBs, and at least GMs are drinking oil (I can't speak for Chrysler).


Tony, are you aware of what a TSB actually is? It is not an indication that ALL the vehicles have the issue, only some. Since GM makes well beyond one million V8's alone yearly there are quite a few out there now. And the important thing to note is that the millions of happy owners are not experiencing any problems. They do not post to the forums!

Like us for instance. A whole pile of Silverados and Savanas, one Express, all either 5.3 or 6.0 gas engines. The vans are used in one of the most demanding duty cycles anywhere, yet NONE HAVE THIS ISSUE. Neither do any of the Silverados.

My sympathies to those with problems, the dealers are never as helpful as they should be. But this is purely internet amplification, the actual numbers are quite small...

 

[lexus114]

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. MDS/AFM/etc. all work by deliberately letting lifters collapse so that the valves stay closed all the time.

There's a misunderstanding that its the electronics that are better than in the 80s. That's true, but that's not why the modern systems work. The modern systems work because they use very small low-power electrical systems (a small oil control solenoid valves) and let high-pressure oil do the actual activation/deactivation. The 80s systems used big solenoids and big wiring harnesses to directly manipulate the engine hardware, and that's why it didn't work reliably.



Thanks for the explanation Magnum. but i still wouldnt want it.

 

[lexus114]

Originally Posted By: jrustles
Originally Posted By: tony1679
Originally Posted By: MolaKule
Me too.

We have a 2008 TrailBlazer with the 5.3L V8 and I have used every oil in the industry, including mine (since it is one of my test mules), and have had zilch oil consumption since new.


So are you saying your 5.3 has AFM but is not having issues? Congrats if that is the case. But if you think I'm wrong, you're mistaken. The only variable that changed was the AFM being disabled. Same oil, same filter, same everything.


Glad the tuner worked out for you! I'd disable AFM at the first opportunity too, TBH

There's just something dumb about continuing to pay inertial and friction costs by dragging the rotating/reciprocating assy around as dead weight to save fuel lol. It just seems like such a backwards way to increase efficiency. Sure, one could work three (or four) cylinders closer to their lowest BSFC, and hope that offsets pumping, inertial and friction losses, but it doesn't strike me as a smart thing to do. It also wears half the engine out more than the other half. At 200K miles, what will we have, one bank with more ring wear than the other? larger bearing clearances on one bank vs the other? more piston pin bore wear?

What about the dragging cylinders, did the engineers really think that the same gas pressure would remain sealed in the closed, dead cylinder?? Ya right, more like it'll stabilize at mid stroke, drawing a vaccuum below half stroke and positive pressure above half stroke. Then there is the oil on the cylinder walls not getting scraped off properly due to no gas pressure on the rings, which could foul up the cylinder with oil. Then there are the unpleasant harmonics...
It's just a weird concept to me, for such an idea to make it to market.


Agree with this post 100%

 

[tony1679]

Originally Posted By: sprite1741
I love my 5.3 with DOD/AFM, as of today I am getting 18.6 mpg in town, haven't been on the highway lately but usually get 28 to 30 mpg on trips to Las Vegas. The speed limit in Idaho is 75 and 80 in Utah. At the most I use 1/3 qt. of oil in 6 mos. The only oil I have used in this engine is Havoline and Chevron conventional and I always use ethanol free premium fuel. No way would I deactivate mine. Have they changed something in the design since 05? Mine is called displacement on demand (DOD), in 06 they changed the name to active fuel management(AFM) but I thought it was name change only.


Yes, it was strictly a name change. Same technology.

 

[46Harry]

I own a 2010 Silverado 5.3 with AFM and I don't have an oil consumption problem with it. A friend of mine has a 2013 Silverado with the 5.3 and it doesn't use oil either. It may have something to do with the higher speeds and mountains encountered in the western states that keeps the AFM from activating very often.

 

[Blue_Angel]

I wonder if something in the engine's history played a part in this behavior, as in maybe an oil was used that fouled the rings somehow and using a different oil can't fix the issue? The TSB about cleaning the rings seems to indicate this, whether or not it works for every vehicle with the issue.

I would be curious to see after driving for an extended period with AFM disabled, if oil consumption returned immediately to its previous excessive level or if it would be any better? In other words, would an extended period of normal operation restore the rings' ability to control oil.

Please don't be so quick to discredit the Engineering that goes into today's cars. Most people would be humbled by the amount of R&D that goes into producing just about any car part let alone an engine.

Just because a few people have an AFM related issue doesn't make it evil, it's just another system amongst hundreds of others that has the potential to fail or cause other problems. It's no different than fuel injection or air conditioning were when they were new.

If there was no clear fuel economy benefit (in the EPA test cycles) AFM or other similar systems would not be in use. Whether your driving reflects those test cycles or not is another issue altogether and has nothing to do with AFM or GM.

 

[sprite1741]

Originally Posted By: 46Harry
I own a 2010 Silverado 5.3 with AFM and I don't have an oil consumption problem with it. A friend of mine has a 2013 Silverado with the 5.3 and it doesn't use oil either. It may have something to do with the higher speeds and mountains encountered in the western states that keeps the AFM from activating very often.


The problem engine is in Oklahoma. I am in the mountains but drive mine to maximize the 4 cyl mode and consider less than 1/3 qt in 5500 miles very acceptable. I never add make up oil as it's still near the top of the hash marks at change time, every 6 mos.

 

[Volvohead]

Originally Posted By: SteveSRT8

My sympathies to those with problems, the dealers are never as helpful as they should be. But this is purely internet amplification, the actual numbers are quite small...


I tend to agree with this.

The AFM thing was talked about at length in another thread here recently. I spent a ton of time looking into the AFM complaints on the GM truck fora before buying ours. There were running changes, starting with top end baffling and then a ring pack adjustment, culminating in '11 with the Dexos oil requirement. I don't think there was a single problem point, but a combination of issues that sometimes combined to cause trouble.

The earlier AFM engines that qualified got progressive updates. That GM had a published diagnostic and repair procedure indicates that the problem was not confined to a few rogue owners. More prevalent complaints among those running extended highway miles in V4. The early problems also seemed to be more prevalent with the aluminum blocks, not that the iron blocks were completely immune. We waited until after '10, because I frankly don't trust the local dealers with this kind of work on an earlier one.

But the few remaining 5.3 complaints after '10 seem to be exactly that - few.

FWIW, our '11 has zero consumption. I've used the range OBD plug around town for the past couple months, only because I got tired of the engine rhythm fluctuations. An eight should feel like an eight, all the time.

I know that the range plug has helped a few earlier engine owners who have had AFM related consumption. It's a safer warranty remedy than a full aftermarket tune.

Like most, the AFM fuel savings is slight at best considering all the equipment involved.

Can't speak to the AFM implementation on the "new" 5.3, however. But I hope that GM would have learned its way with AFM by now.

 

[wag123]

Not only are GM's and Chrysler's cylinder deactivation systems plagued with known problems (indicated and admitted-to by all of the manufacturer TSBs that have been issued), but Honda is also having problems with theirs, and some people believe that Honda is THE advanced engine technology leader/expert. So, that makes it a clean sweep, ALL of the manufacturers that use this technology are admittedly having problems with it.
Personally, I don't like the way that any of these engines react/respond in real-world driving conditions, and I wouldn't hesitate for one second disabling this "feature" if I owned a vehicle that had it.

 

[fdcg27]

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.


The Wright's buddy asked the brothers that since that flying thing didn't work back in the '80s for others, why would they even consider it now?
Technical development has made many things possible today that couldn't be made to work thirty years ago.
You're using one to view this thread right now.

 

[zuluplus30]

Originally Posted By: Ken2
Quote:
If I was to EVER buy another AFM motor...
What has GM done to earn your future business?


Nothing. I've owned 3 GM vehicles over the last 8 years and they have all been meager at best. Reliability and resale are huge for me and neither my Malibu or 2 Silverados would win any awards in either of those departments. That's why I have 2 Honda's in the driveway now....

 

[zuluplus30]

Originally Posted By: SteveSRT8
My sympathies to those with problems, the dealers are never as helpful as they should be. But this is purely internet amplification, the actual numbers are quite small...


I felt the exact same way. I pitied the 07-08 owners who got the raw end of the deal......

I'll never forget the day I checked the oil to see it down a full quart in 3000 miles in our '09. Never burned a drop until that point. It only got worse from there. By the time I got Chevy to fix it, I had failed a consumption test to the tune of 2.5 quarts in 2000 miles. The numbers were obviously large enough of a probelm for GM to issue multiple TSB revisions chasing a common fix. Of everybody I know with a 5.3 AFM in any platform, I'd estimate 10-15% have a consumption problem. None past 2011 that I'm aware of however.

 

[jrustles]

To Steve and all others with no issues with AFM, how much time do your vehicles spend in the mode?? Sporadically or a lot? How much steady cruising do you guys do?


Honestly, I think this tech was chosen and applied as an effort to augment advertised fuel economy. It undoubtedly helps the EPA test cycle, and I'd put money that it's designed around it. It may go unnoticed as an issue until close to/the end of warranty, and even in warranty, you still have to get past the arbitrarily set 'acceptable consumption' trap. The only way for warranty work to really happen, is if something goes seriously wrong due to the issue. I'd bet the engineers themselves personally think it's a bad idea, but get as the day is long, engineers hands are forced by corporate.

 

[MolaKule]

Quote:
To Steve and all others with no issues with AFM, how much time do your vehicles spend in the mode?? Sporadically or a lot? How much steady cruising do you guys do?


In our case, cruise mode is 90% of the time.