Oil Burning 2013 GMC
 

Very frustrated with my 2013 GMC Truck. From day one its been burning oil. Now it uses around 1 quart every 1000 miles!!!! I have been researching this issue and so far it looks like the AFM Active Fuel Management is the problem.


For years, GM has touted the AFM system as their way to save consumers fuel. The system basically shuts down cylinders when not in use meaning that a V-8 is a V-4. It isn’t a new technology and has been around since the end of WWII. Yet, for the last several years that GM has used it, owners have complained about excessive oil use.
What causes the Oil Loss?

The owners that have reached out to us and the complaints we have read about say that the AFM is directly responsible for the problem. Many of them have bought after-market tuners to deactivate the system which they claim stops the loss. The reason seems to be that when the engine deactivates a cylinder, the oil doesn’t simply sit in the head, it either gets pushed out of the shaft or soaks into the rings. This then causes a loss of oil.

Officially GM says:

This condition may be caused by two conditions. Oil pulled through the PCV system or oil spray that is discharged from the AFM pressure relief valve within the crankcase. Under most driving is discharged from the AFM pressure relief valve within the crankcase. Under most driving conditions and drive cycles, the discharged oil does not cause a problem. Under certain drive cycles (extended high engine speed operation), in combination with parts at the high end of their tolerance specification, the oil spray quantity may be more than usual, resulting in excessive deposit formation in the piston ring grooves, causing increased oil consumption and cracked or fouled spark plugs (#1 and/or #7).

GM has issued a fix for this which is a shield that keeps the oil from disappearing. What’s a bit surprising is that GM’s latest TSB addressing this issue was released on January 3, 2013. It addresses the problem in 2007-11 trucks with the new shield.
Source Chevy/GMC AFM Cylinder Deactivation Excessive Oil Consumption | Tundra Headquarters Blog

This week I'm going to try to see if by running it in manual shift mode and keeping it out of 6 gear, I will see any difference in oil consumption and fuel mileage? By doing this I noticed it doesn't drop into 4 cylinder mode.

Check the GM forums. There's got to be a simpler way to disable it.

Is there a reason you're not working with your dealer on this? Left valve cover, rings, afm solenoid assembly, afm shield.... Once they run through their regular suspects, if your oil consumption is still excessive they'd rather put another engine in it than take it back as a lemon

I'm defiantly going to take it back and have them look at it. Its just really frustrating to have a new truck that only has 32k on it and have to pack around oil and be checking the oil level every fill up.:mad:

My 02' 8.1 liter Silverado 3500 consumed half a quart of oil every 1,000 miles until it reached 60k+ on the odometer, then it stopped using any excessive amounts of oil between changes. My wife's 2010 Avalanche 5.3 liter never uses any oil and she's at 30k+ miles. There a long history with GM V-8's and oil consumption.
My advice be persistent but patient with the dealer. This issue is likely to go several rounds before you get service.

One other thought, it may not be the AFM system causing the issue. Chevy/GM has continue to use those really hard piston rings for several decades. Those rings have a very long break in period to properly seat in the cylinder walls. Try running to 10% or less on the oil life monitor before changing oil, especially since you are adding 2 to 3 quarts during the oil life cycle. If you continue to have AFM issues get the shield checked out. It could be poorly installed or sealed. However, I've noted my wife's Avalanche not moving to v-4 when I expected it too, and she's not having any oil usage problems.

Check inside the intake and PCV hose for oil, that's the easiest way to check to see where your oil is going. That's a ridiculous amount of burned oil for such a new truck.

Take off the air intake tube, hold open the throttle, and shine a flashlight inside. Some 5.3s will have a lake of oil laying in the intake, even ones w/o customer complaints( not to say they aren't burning oil)

Update:

I have been doing a test since my last oil change. I'm no longer using OD and keeping the gear selector in manual 5th gear. The results are not one drop of oil being used.:thumbup:

I did some research and all I can say it sounds like to me GM doesn't have a handle on this oil consumption issue.:mad:

Anyway my fuel mileage has drop about 1 mpg. So I'm going to live with this.

Should be able to disable the AFM, a nephew has a friend that did on his Camaro and barely noticed any change in MPG.

This is what I'm going to do after I get a few more miles on it.

I would highly suggest a "catch can" on the pcv system. I made a cheap one out of a water supply sediment filter and some fittings for under $50. In 5k miles it will catch maybe half a quart, and thats not even all of it, i need to make more modifications to it.

If I ever built/ran an LS3 series engine it would not have AFM for this reason alone.
Fuel mileage up, but oil mileage way down, not a good trade IMO.

If you were burning that much oil your catalytic converter is likely well on its way to being clogged with oil additive ash.

On the older ones this was a fix to some degree. After talking to a GM mechanic "off the record", he said my truck already has the supposedly fixed items. He said its the design of the cylinder deactivation that is the cause. When the deactivated cylinder runs through its deactivation cycle the rings are floating and not sealing oil because there's no combustion to expand them to the cylinder wall, and this lets oil gets past the top ring. This also causes the ring pack to get gummed up in a hurry and then it even makes the problem compound itself.

IMHO the design was a complete failure from the beginning. GM knows this and also knows what the cost would be to fix it. Can you say another Bankruptcy. :mad:

It looks like a good trade off: A gain of several mpg in normal driving at the expense of having to add a quart of oil periodically.

A lighter oil, maybe letting the additive chemists have a go at it first might be the easy part of the fix. Getting Murricans to check critical fluids once in a while will be the hard part of the fix.

Once reformulated oil is developed and put in the pipeline, the recall would simply be a matter of getting folks in for a free oil change (make it a flush) and a pamphlet explaining the new oil specification. It'll be a bonanza, not a bankruptcy: how many maintenance items are going to get sold at the same time people are in for the "free oil upgrade?"

Motor oil has been reformulated at least 5 times since the 1980s.
Each reformulation pulls more and more anti-wear additives and detergents out of the oil.
There are around 1/2 to 1/3 the anti wear additive and as little as 1/4 the detergents found in the old formulations.

Pulling additives out of the oil is not an oil up grade, it is in fact an oil down grade.
This is a prime example of just because something is new doesn't mean its better.

I say gut the converter if you can get away with it and run SH or SJ oil.
SH oil was formulated when petro chemical and automotive engineers only cared about the oil doing 2 things, 1 minimizing wear and 2 protecting against sludge build up.

Just like the first time they tried it in the 1970s.
But back then the oils were loaded with detergents so the piston rings never gummed up with crud.