Anybody have 5.3 start consuming oil after a tune to disable AFM?

SouthCo · August 11, 2012

Ok, I have a 2010 sierra with 5.3 and AFM. It has the LC9 with aluminum blocks and heads. So far I have just shy of 12k miles and it doesn't consume any oil. I'm thinking of tuning to get rid of AFM to head off any future problems with oil consumption.

Has anybody without oil consumption issues turned off AFM via a tune and still ended up consuming oil?

Zembonez · August 11, 2012

I've dealt with a ton of people who have a BB tune and nobody has ever mentioned any oil consumption changes. The tune simply stops the system from activation... so the mechanical bits are all still there. Should have zero effect. Unfortunately deactivating it won't keep it from consuming oil. If it's going to happen it will - on or off.

SouthCo · August 11, 2012

Just looking for some real world results. Most threads blame the oil consumption on afm kicking in, so that's why I wonder if anyone experienced it even with it off. I've read about oil deposits building up on bottom of deactivated pistons causing ring issues. IDK, but curious.

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Zembonez · August 11, 2012

I understand. Not trying to rain on your thread. Just adding to it.

BlackZ71Silverado · August 11, 2012

I've dealt with a ton of people who have a BB tune and nobody has ever mentioned any oil consumption changes. The tune simply stops the system from activation... so the mechanical bits are all still there. Should have zero effect. Unfortunately deactivating it won't keep it from consuming oil. If it's going to happen it will - on or off.

Going to have to STRONGLY disagree with this statement. That's like saying a loaded gun lying on the table will fire on it's own because there is a round in the chamber. Unless someone pulls the trigger is will not fire.........

The issue with oil consumption is the blow by that is caused by the cylinder shut down when the AFM activates.

The GM service bulletin tells dealerships how to put a band aid on this by modifying some internal part of the afm system. They install a reflection shield that is meant to stop the oil blowby when it switches between modes, to help stop/slow down consumption.

With it deactivated, you are taking the blow by out of the equation because you are not allowing cylinders to shut down.

Here's one for you to think about...My brother has a 2010 Silverado 5.3L CC with 30,000 miles. Started using oil at 10,000 miles, about a quart between changes. Installed a Superchips tune at 17,500 and deactivated AFM. NO more oil consumption.

Not trying to argue but that facts are the facts. It's not hard to realize what the issue is here and it's not just GM. Trucks with AFM disabled through a tune=no oil consumption. Trucks with factory tune=oil consumption........end of story

Zembonez · August 11, 2012

To each his own I guess.

BlackZ71Silverado · August 11, 2012

Last post since this is a poll :

...My post if factual NOT opinion. If the system that causes the blow by/consumption is not active, it can't cause consumption.....Funny how us guys with it tuned out don't have this problem and those with it working from the factory are seeing usage.

Zembonez · August 11, 2012

Like I said... you are welcome to have your opinion. What else do you want?

txab · August 11, 2012

Z45 · August 12, 2012

IMO

All you need to do is get one look at the pistons from from a AFM engine that was using oil and you know its (AFM) the problem. The pistons in the cylinders (that shut down) overheat when they are not working and cook the oil right onto the piston and the rings. The dealers have to send those parts back to GM but one dealer friend showed me one of them once. You could hardly tell there were any rings on this piston they were so caked up with carbon. This one engine came from one of their salesman's 2008 Sierra CC. I recall he said it had about 40K miles. Trouble is, the longer the engine lives on AFM, the more the engine has to develop the deposits on the piston and rings.

Every AFM engine has the chance to develope this problem. The only things stopping (besides disabling) it from happening are; using better oil, or driving more aggressive (keep it in 5th gear) so AFM is used a smaller percentage of the time.

They are never going to do anything about it because the name of the game is fuel economy and anything that gives them any mpg improvement for CAFE is what is the most important. Oil burning is a acceptable problem as long as there are mileage improvements.

Don't think its just GM, I have a custome with a new Furd ecoboost, he says he uses oil?

5829BMG · August 12, 2012

IMO

All you need to do is get one look at the pistons from from a AFM engine that was using oil and you know its (AFM) the problem. The pistons in the cylinders (that shut down) overheat when they are not working and cook the oil right onto the piston and the rings. The dealers have to send those parts back to GM but one dealer friend showed me one of them once. You could hardly tell there were any rings on this piston they were so caked up with carbon. This one engine came from one of their salesman's 2008 Sierra CC. I recall he said it had about 40K miles. Trouble is, the longer the engine lives on AFM, the more the engine has to develop the deposits on the piston and rings.

Every AFM engine has the chance to develope this problem. The only things stopping (besides disabling) it from happening are; using better oil, or driving more aggressive (keep it in 5th gear) so AFM is used a smaller percentage of the time.

They are never going to do anything about it because the name of the game is fuel economy and anything that gives them any mpg improvement for CAFE is what is the most important. Oil burning is a acceptable problem as long as there are mileage improvements.

Don't think its just GM, I have a custome with a new Furd ecoboost, he says he uses oil?

Bingo

JaBradt85 · August 13, 2012

Hondas with deactivation also use oil.

kdixer · August 15, 2012

Not trying to argue, just trying to understand. So I have two questions concerning the above theories.

How does a deactivated cylinder cause more blow by than an active cylinder?

The piston is traveling up and down regardless. For it to cause more blow by the deactivated cylinder would have to be allowing gasses past the rings and into the crank case. This would happen no matter if the cylinder was deactived or not.

What is causing the piston in a deactivated cylinder to over heat?

From what I understand the valves deactivate before the exhaust stroke trapping the combustion gases in the cylinder. This creates an "air spring" effect in that piston to counteract the friction of the piston moving up and down. The absence of a combustion event in a deactivated cylinder should more than compensate for all other thermal factors.

Doug_Scott · August 16, 2012

Not trying to argue, just trying to understand. So I have two questions concerning the above theories.

How does a deactivated cylinder cause more blow by than an active cylinder?

The piston is traveling up and down regardless. For it to cause more blow by the deactivated cylinder would have to be allowing gasses past the rings and into the crank case. This would happen no matter if the cylinder was deactived or not.

What is causing the piston in a deactivated cylinder to over heat?

From what I understand the valves deactivate before the exhaust stroke trapping the combustion gases in the cylinder. This creates an "air spring" effect in that piston to counteract the friction of the piston moving up and down. The absence of a combustion event in a deactivated cylinder should more than compensate for all other thermal factors.

I think what they really mean is that the cylinder/piston does not stay hot enough to heat the oil so it can run off.

The spring effect you mention would disapate within seconds. At 2k rpm, that cylinder's piston compresses 33 times a second. With valves not operating, every upward stroke is a compression stroke. Cylinder leakdown would eliminate the "spring effect" fast. Doubt there is any left after the first second. You may have stumbled onto something though. If they in fact trap combustion gases, those gases will leak down into crankcase. Perhaps that is causing the buildup of carbon/crap on piston?

BlackZ71Silverado - As for an opinion being "fact", it takes more than just anecdotal evidence to prove a fact.

BlackZ71Silverado · August 16, 2012

One more time............didn't say opinion = fact, go back and re-read.......I posted what my experience was with the trucks and oil consumption. It was no opinion at all that oil consumption stopped after the AFM was tuned out, it was FACT in the case I mentioned....Not hard to understand. If you like your AFM good for you, I don;t like it, it causes nothing but issues so it's tuned out, no more issues.