GMC Sierra 2500 HD L8T 6.6 gas - First UOA, PUP 5W-30, 4,500 miles

[kschachn]

Mobil-1 EP Triple Action. It won't shed viscosity (shear) as fast.
I used to run Pennzoil Ultra Platinum. Complained about their ending cst@100 many times.

How will that help with fuel dilution? This isn’t mechanical shear of the VM.

 

[Shatterz]

Op- How did you break in when you bought the truck? It seems like you are a fastidious, focused owner.

I have a v10 and others that are a quart per 1000 miles users. I have no problem with oil consumption anymore. It used to bother me, then one of my BMWs took me from 140k miles to just under 400k, before a wreck, and had the same consumption 1q/ 900 miles throughout. That vehicle retrained its owner. One of my cars uses no oil between changes and it actually has me suspicious. FWIW.

Break in was easy and variable speed driving for the first 1000 miles. After 1000 miles some brief full throttle runs once throughly warmed up with just regular driving and then first oil change at 1500 miles. Truck didn't tow anything for quite a while and really only ever sees tow about 4-5 times a year with a heavy maxxed out tow once a year.

On a side note the transmission developed a slight harsh 2-3 shift back in January. I thought i was just imagining things it was so slight. Fluid was clean and checked level ( as per gm instructions from plug underneath, slight drip in park with engine running and temp over 122f). Well one frigid cold February morning on the way to work 2-3 shift just slipped quite a bit. Later that afternoon I left work early to drive to a friends shop who does transmissions to just put our heads together before I go to the dealership. Well the trans blew at a stop light on the way there. 38k miles and it was flat-bedded and would be without it for 3 week (complete re-build with torque converter, valve body, clutch packs everything). They had never seen a 6L90 go like that on a non abuse truck.

 

[burbguy82]

How will that help with fuel dilution? This isn’t mechanical shear of the VM.

do you have any evidence, or scientific studies, that would refute that m1 would not be better in this application?

 

[burbguy82]

Break in was easy and variable speed driving for the first 1000 miles. After 1000 miles some brief full throttle runs once throughly warmed up with just regular driving and then first oil change at 1500 miles. Truck didn't tow anything for quite a while and really only ever sees tow about 4-5 times a year with a heavy maxxed out tow once a year.

On a side note the transmission developed a slight harsh 2-3 shift back in January. I thought i was just imagining things it was so slight. Fluid was clean and checked level ( as per gm instructions from plug underneath, slight drip in park with engine running and temp over 122f). Well one frigid cold February morning on the way to work 2-3 shift just slipped quite a bit. Later that afternoon I left work early to drive to a friends shop who does transmissions to just put our heads together before I go to the dealership. Well the trans blew at a stop light on the way there. 38k miles and it was flat-bedded and would be without it for 3 week (complete re-build with torque converter, valve body, clutch packs everything). They had never seen a 6L90 go like that on a non abuse truck. View attachment 219125

my 2020 had a bad tq converter from day 1. much of particles in the pan at 5000 miles. dealer said this was normal, i am guessing you have the same issue. tranny will be junk. i got rid of my personal truck

 

[Big_B]

Hmmmm. This has me worried now. My truck with the 6L90 just started to do the same thing.
31,000 miles.

 

[Shatterz]

Hmmmm. This has me worried now. My truck with the 6L90 just started to do the same thing.
31,000 miles.

It’ll just be a matter of time unfortunately. I had a really good master tech do my re-build at a reputable GMC dealer, actually got to talk to him and see the trans apart along with stopping back a few days later to see it getting re-built.

I believe my torque converter was defective since day 1 and it took 38k miles for it to finally eat itself. Truck now shifts and feels better than it did since I picked it up brand new with 2 miles on it. The final thing that happened before things all went ka-boom was fuel mileage went to complete ****. I have super heavy true 35x11.5R20” Toyo RT open country which don’t help but right before it failed I was getting sub 10 mpg mixed driving. Now I’m back to 12-13 mpg mixed

 

[Tsmith967]

I know im late to the party, but I was reviewing these UOA's because we have had serious problems at work with them. According to Isuzu, 1 quart for every 100 gallons of fuel is normal for these. We have also seen several come apart on the bottom end already with under 30k miles.

 

[burbguy82]

normal

which is ridiculous

 

[Tsmith967]

which is ridiculous

Thats GM for you. I know I am biased, but still. We replace countless 6.0, 6.6, 6l90, and 89l0's.