Afm And Oil Consumption

98 Z71 SLT · February 6, 2011

E85 vs regular gas really has nothing to do with it.

AFM is the culprit. Shutting down 4 cylinders for extended amounts of time doesn't help anything. Cooling happens,then oil is chunked onto the rings. Then the rings don't seal, creating oil usage.

Did the 99-06 5.3 burn oil??? Nope. They had cold knock and a random set of heads were junk, but other than that, the 5.3 was a legendary powerplant. Until 07.

mtiffinal · February 6, 2011

Super StealthPosted Today, 06:07 PM AFM is the culprit. Shutting down 4 cylinders for extended amounts of time doesn't help anything. Cooling happens,then oil is chunked onto the rings. Then the rings don't seal, creating oil usage.

Wonder why all the trucks with AFM aren't having problems?

BlackZ71Silverado · February 6, 2011

Super StealthPosted Today, 06:07 PM AFM is the culprit. Shutting down 4 cylinders for extended amounts of time doesn't help anything. Cooling happens,then oil is chunked onto the rings. Then the rings don't seal, creating oil usage.

Wonder why all the trucks with AFM aren't having problems?

Maybe because a lot of us have the AFM turned off with a tuner?

98 Z71 SLT · February 6, 2011

Alot of guys have turned off the capability of AFM with a tuner, as stated above.

Alot of guys just don't know they are using oil

Alot of guys do a majority of city driving, where AFM generally isn't commanded on

Is EVERY 5.3 burning gallons of oil?? No. But ALOT are. GM has to see a certain number of complaints in order to issue a TSB.

Last time I looked, there were multiple TSB's on the AFM system, and oil burning.

jimbrown1 · February 6, 2011

My 2011 Silverado with the 5.3 and AFM seems to switch to V4 mode when I drive around town, but I don't keep my foot in the gas either. I'm planning to turn off AFM below 60 mph so this doesn't happen again, as soon as Justin returns my tunes to be put on the truck via Auto Cal. Can't wait!!!!

Alot of guys have turned off the capability of AFM with a tuner, as stated above.

Alot of guys just don't know they are using oil

Alot of guys do a majority of city driving, where AFM generally isn't commanded on

Is EVERY 5.3 burning gallons of oil?? No. But ALOT are. GM has to see a certain number of complaints in order to issue a TSB.

Last time I looked, there were multiple TSB's on the AFM system, and oil burning.

SouthCo · February 6, 2011

E85 vs regular gas really has nothing to do with it.

AFM is the culprit. Shutting down 4 cylinders for extended amounts of time doesn't help anything. Cooling happens,then oil is chunked onto the rings. Then the rings don't seal, creating oil usage.

Did the 99-06 5.3 burn oil??? Nope. They had cold knock and a random set of heads were junk, but other than that, the 5.3 was a legendary powerplant. Until 07.

AFM will not shut down to 4cyl but for a specified amount of time. I forget what it is, but it will only stay in 4 cycl mode for so long and it goes back to 8 cycl regardless of engine load or foot pressure.

Savagecanuck1 · February 6, 2011

2008 5.3 4.10 with AFM.I use synthetic oil and never add between oil changes and use the OLM.My old 01 2500HD with the 8.1 was an oil burner.I live in the mountains and pull a small work trailer so the AFM is never on for long

spfish · February 25, 2011

I would like to weigh in just a little bit. Just for data and documentation.

2008 Suburban LTZ with LC9 engine (5.3 AFM Aluminum block), 88,000 miles now

Mobil 1 synthetic oil since very first oil change. Change oil when DIC says to (6000-8000 miles).

Paid mechanic (NOT dealer) to do oil changes (only one guy has ever changed the oil until the last one). He NEVER told me that the oil level was low going into a change so I didn't think I had an oil consumption issue. Suddenly at about 72,000 miles the ZERO OIL PRESSURE warning came on and scared me to death. I've been driving for 32 years and I have NEVER EVER had that happen before.

Since 72,000, I've been adding a qt of synthetic about every 3-4,000 miles. That, too, has never happened with ANY vehicle I have ever owned. So this really bothered me and I started keeping up with it.

I also have the lifter click at start up for about 5-10 seconds. Idles fine, smooth.

I get 15 mpg city and 18 highway.

Tailpipe has a jet-black dusty ring around it. Sounds to me like if this is an AFM issue, the oil is pushing into thsoe cylinders and slowly cooking off on its way out of the vehicle. I NEVER see smoke. Not at startup, idle or run. Someone told me that synthetic won't smoke. Not sure if that is true or not.

And since I'm just talking now, I wanted an HD pickup with the diesel to tow my boat. Wife said she didn't want to hear the diesel. Now I'm divorced and wish to heck I hadn't listened to her. I kept the boat. Gave her up.

Have read a few places on here, "I love my truck, but I wish it didn't burn oil." DITTO! I don't care what ANYONE says, a 2008 model truck that cost $55,000 should NOT burn a qt of oil ever 3,000 miles. If GM says that's normal, then that's part of why GM has been in bad trouble. My 1999 K1500 Suburban ran to 180,000 miles and never used a drop of oil. The tranny gave out after pulling that 6,000 lb boat and trailer. But never used oil. My 1994 C1500 Suburban ran to 150,000 miles and never used a drop of oil. This one disappoints me but my loyalty is to GM so I guess I'm going to stay put.

music · February 25, 2011

While I agree that the motor shouldn't burn any oil, I must ask the obvious. What does it really hurt? If I drive 3000 miles @ 16 mpg, that's 188 gallons, or 750 quarts of fuel. Last I checked, gas comes from the same feed stock as motor oil. I'd rather not have to add oil between changes, but I've done it before on other cars.

However, if oil consumption is pointing to a fundamental problem (poor ring fit, corroded valve....), then that points to poor performance (low compression, etc). I think that's why GM (and every other manufacturer) has the "maximum oil rate tolerance" that seems so high to us. They know that their manufacturing methods are not good enough for every motor to have a perfect fit, and a few are actually expected to burn that much. This is true for Toyota, Ford, etc. too; i.e., they have a similar "acceptable oil consumption" policy.

If anything, my money is on the idea that AFM can make an existing fitment problem worse, but that it is not the root cause. The lifter tick that some 07's / 08's showed may well be specific to the AFM lifter used at that time, but I haven't experienced it myself.

pm26 · February 25, 2011

I would like to weigh in just a little bit. Just for data and documentation.

2008 Suburban LTZ with LC9 engine (5.3 AFM Aluminum block), 88,000 miles now

Mobil 1 synthetic oil since very first oil change. Change oil when DIC says to (6000-8000 miles).

Paid mechanic (NOT dealer) to do oil changes (only one guy has ever changed the oil until the last one). He NEVER told me that the oil level was low going into a change so I didn't think I had an oil consumption issue. Suddenly at about 72,000 miles the ZERO OIL PRESSURE warning came on and scared me to death. I've been driving for 32 years and I have NEVER EVER had that happen before.

Since 72,000, I've been adding a qt of synthetic about every 3-4,000 miles. That, too, has never happened with ANY vehicle I have ever owned. So this really bothered me and I started keeping up with it.

I also have the lifter click at start up for about 5-10 seconds. Idles fine, smooth.

I get 15 mpg city and 18 highway.

Tailpipe has a jet-black dusty ring around it. Sounds to me like if this is an AFM issue, the oil is pushing into thsoe cylinders and slowly cooking off on its way out of the vehicle. I NEVER see smoke. Not at startup, idle or run. Someone told me that synthetic won't smoke. Not sure if that is true or not.

And since I'm just talking now, I wanted an HD pickup with the diesel to tow my boat. Wife said she didn't want to hear the diesel. Now I'm divorced and wish to heck I hadn't listened to her. I kept the boat. Gave her up.

Have read a few places on here, "I love my truck, but I wish it didn't burn oil." DITTO! I don't care what ANYONE says, a 2008 model truck that cost $55,000 should NOT burn a qt of oil ever 3,000 miles. If GM says that's normal, then that's part of why GM has been in bad trouble. My 1999 K1500 Suburban ran to 180,000 miles and never used a drop of oil. The tranny gave out after pulling that 6,000 lb boat and trailer. But never used oil. My 1994 C1500 Suburban ran to 150,000 miles and never used a drop of oil. This one disappoints me but my loyalty is to GM so I guess I'm going to stay put.

The problem is that the maximum acceptable oil consumption rate will be artificially adjusted based on the worst case they see, which gives GM a way out of having to repair a defective product. Nobody will convince me that 1 quart per 1,000 miles is acceptable oil consumption for a low mileage engine. Yet it seems that several people who complained about high oil consumption were told just that.

I draw a line at 1 quart per 3000 miles, and this seems to be about the highest acceptable oil consumption rate for new engines based on many expert opinions.

music · February 25, 2011

Nobody will convince me that 1 quart per 1,000 miles is acceptable oil consumption for a low mileage engine. yes it seems that several people who complained about high oil consumption were told just that.

I think the GM spec is 1 qt per 2000 miles. The Toyota spec I've seen is 1 qt per 1000 miles.

browning22 · March 1, 2011

2007 Chevrolet Silverado 1500 LTZ 5.3AFM Aluminum Block

Started burning oil around 100k and smoking real bad.

Burning 1 Qt. of oil every 1500 miles.

Deflector plate installed per TSB at Chevrolet place for 699. Included plugs, oil, part, carbon cleaning, etc.

Still Burns 1 Qt. per 1500 miles now.

I cut AFM off last Friday. Truck is still smoking when I start it up. Not sure if the oil that had previously passed through is still causing it to smoke, not sure.

I have driven about 700 miles since turning AFM off. I will check today and see how much oil it has lost.

music · March 1, 2011

Deflector plate installed per TSB at Chevrolet place for 699. Included plugs, oil, part, carbon cleaning, etc.
Still Burns 1 Qt. per 1500 miles now.

Why perform the TSB without first diagnosing the cause using the "consumption diagnosis TSB"? I'd check typical oil-burning issues first (e.g. compression) before spending $$ on afm part updates. It's the last thing checked in the diagnosis (least likely cause).

browning22 · March 2, 2011

Deflector plate installed per TSB at Chevrolet place for 699. Included plugs, oil, part, carbon cleaning, etc.
Still Burns 1 Qt. per 1500 miles now.

Why perform the TSB without first diagnosing the cause using the "consumption diagnosis TSB"? I'd check typical oil-burning issues first (e.g. compression) before spending $$ on afm part updates. It's the last thing checked in the diagnosis (least likely cause).

I don't fix them. I just took it in and told them what it was doing and they told me that I needed the deflector plate. They did not start me on an oil consumption test or anything like that.

music · March 2, 2011

I don't fix them. I just took it in and told them what it was doing and they told me that I needed the deflector plate. They did not start me on an oil consumption test or anything like that.

I guess I was posting for others sake as much as anything. I wouldn't let them perform an expensive TSB repair on my dime without first diagnosing/tracing the problem to that particular "fix".