37K on 2012 5.3L GMC Sierra

Bad Bowtie2 · September 17, 2014

I just picked my truck up from the local dealer. She has 37,400 on the clock now & just ran out of the 3YR/36K bumper to bumper warranty.

They were doing an oil consuption test for me under original 36k warranty.

I noticed 18K ago I was a little low (maybe 1/2 a qrt) on oil during one of my 6K oil changes. I do my own oil changes & use Mobile one with a GM oil filter.

Then 12K ago I noticed I was close to a quart low. Then 6K ago I had to add a quart & the dipstick still said I was 1/2 qrt low!!

Any hoo, after my dealer documented I was using roughly 1/2 quart every 500miles, on my last oil change, GM had them tear down the 5.3L motor.

So 8 new pistons, a bearing set, a new ring set, many seals, new head bolts, new left valve cover, coolant/oil, etc later here I go again. The tech wanted to see me when I picked my GMC up today. He kept all the old, original parts until I came to get my truck before he turned them in (GM warranty thing).

He knew I ran Mobile 1 oil & advised me to stop starting with this new overhaul. He told me some of the AFM 5.3L engines like this oil & some do not.

I have never heard this before!!

I looked at a box with my old pistons in them & they looked like they had 95K+ on them & poor maintence!! Burnt up cooked oil all over them, side, top, skirts EVERYWHERE!! It was crazy looking!!

I religiously changed my oil every 6K and added a can of SeaFoam to my gas tank. Up until this last year I had been running PURE unleaded in my truck too. It's hard to find it in this area now.

I wish I had taken a pic of these nasty pistons. I guess I was in such shock at what I saw.

Has anyone else here been told "Mobile 1" oil is bad on the 2007.5-2013 GM trucks with AFM?

DaveH71 · September 17, 2014

What did he suggest you use? I don't see why it would matter what oil it is if its getting pulled into the deactivated cylinders when AFM is on and being burned.

I would suggest you get the AFM turned off until GM finds out a real fix instead of GM blaming everything on mobil 1.

2017SierraSLT · September 17, 2014

I'm not a fan of Mobil 1 oil. I have been using Pennzoil Ultra since 1000 miles. I changed it again at 5000, and I am at 8200 now. I will change it at 10k. It does not consume oil. I shut off the AFM at 1000 miles. This thing runs great, and it should with the low miles.

DaveH71 · September 18, 2014

I'm not a Mobil 1 user either, i use Redline. The oil isn't the problem though, it's the poorly designed AFM system. Any oil is going to burn in those cylinders.

Bad Bowtie2 · September 18, 2014

What did he suggest you use? I don't see why it would matter what oil it is if its getting pulled into the deactivated cylinders when AFM is on and being burned.

I would suggest you get the AFM turned off until GM finds out a real fix instead of GM blaming everything on mobil 1.

GM's Dexos blend....

I drive this 2012 GMC Sierra in town 80% of the time. I use my manual select 5th gear religiously, since my speeds are mostly under 50MPH.

Out on the by-ways & highways (50+ mph) I let AFM do it's thing in 6th gear...

DaveH71 · September 18, 2014

Range makes a pretty cool AFM disabler that plugs into your OBD port. You can go back to stock instantly just by unplugging it. If i had AFM on my 6.2 it's what i would be using.

Dans Denali · September 19, 2014

I would be more suspicous of the SeaFoam than the oil. Don't our owners manuals say that no fuel additives are suggested or needed? Mobil 1 is well proven and the only approved oil of many exotics like Porsche.

Dan

butzers09silverado · September 20, 2014

I have been running mobil 1 in my 2009 which is the same engine as yours minus the deflector shield (i don't have that) and i've been running for 95,000 miles. I've run mobile in every vehicle i own except our diesel grand cherokee.

Bad Bowtie2 · September 24, 2014

I think I'll go back with Mobile 1 then. It is still a GM "approved oil".

If anything, I still have a 100K powertrain warranty.

Tony1959 · November 24, 2014

I'm not a fan of Mobil 1 oil. I have been using Pennzoil Ultra since 1000 miles. I changed it again at 5000, and I am at 8200 now. I will change it at 10k. It does not consume oil. I shut off the AFM at 1000 miles. This thing runs great, and it should with the low miles.

Tony1959 · November 24, 2014

2013sierrasle, by what method did you turn off the AFM?

chupe442 · November 24, 2014

Never a big Mobil1 guy but then again my world has always been Valvolene products... I would think that any issue you have internally would not be subject to Mobil1 but more so toward the Seafoam in every tank. I can see a can once or twice a year for the injector cleaning but not every tank.

With a fresh motor for the most part, my suggestion would be to get a tune and disable the AFM all together.. Many guys love the Range plug and play but there are issues with them as well. I have yet to see a bad thing with Black Bear Performance... My 2 cents. I have a Black Bear tune and would do it again in a heart beat!