What did you do to your NBS GMT800 Tahoe/Yukon Today?

[Tonyrodz]

I think there'd have to be a gaping hole in the filter to get enough dirt to cause that much sludge. I would recommend using a high mileage oil (I would suggest Mobil 1 brand since it's worked well for me) and see if your sludge issues continue. That's the only difference obvious to me between your sludge issue, and my lack of sludge.

Does the high mileage oil have extra detergents in it? What's different about it?

 

[clandr1]

Does the high mileage oil have extra detergents in it? What's different about it?

Here's a pretty succinct summary I found online. This could all be snake oil for all I know, but it's worked for me so I'm sold on it, even if it is nothing more than a placebo.

What makes high-mileage engine oils different?

High-mileage oils have ingredients to take care of older engines, like conditioners, seal swells, antioxidants, detergents and wear or friction additives. Typically they use a viscosity modifier that is durable and won’t lose viscosity very easily. These oils need to stay thicker longer to protect engine parts.

Here is a longer description from the Mobil 1 site:

PdsDetailsPage

Mobil 1™ High Mileage oils are advanced full synthetic motor oils designed to help extend the engine life of vehicles with over 75,000 miles and to protect for up to 10,000 miles between oil changes*.

www.mobil.com

 

[smcnair]

If anyone actually SOLD this stuff I would buy some. But the only places that do have BG products will not sell them. They will only perform service with BG products.

Amazon.com

 

[NoReverseYukon]

Amazon.com

$336 !!!
Uh, no.

 

[iamdub]

Got my oil pan dropped today and that sumbitch is FULL of sludge! Boy am I pissed. I COMPLETELY cleaned this pan out when I replaced the gasket and pickup tube in 2017. Since then I have changed the oil every 5,000 miles with Amsoil XL series oil and either a Mobil1 filter or a Wix XP filter. I'll admit though, the last 2 oil changes I used Mobil1 oil and then Walmart Supertech Full Synthetic for the last oil change. (about 3 months ago). In the bottom of the pan there is a THICK mud like sludge, and on the baffle, there is some hard caked up sludge that is flaking off in chunks kind of like rust. It also has a slight metallic color to it. Can anyone with more insight than me explain WTF is going on here?

How does the rest of the engine look? Same sludge caked on the inside of the block, on the crank, end caps, etc? Once you pull that timing cover, you'll know if it's the engine or if it's the quality oil you're using doing its job. I'm betting/hoping it's just sludge that's been dissolved off the innards by the detergents in the oil. Do this mill have a persistent coolant loss?

 

[ScottyBoy]

How does the rest of the engine look? Same sludge caked on the inside of the block, on the crank, end caps, etc? Once you pull that timing cover, you'll know if it's the engine or if it's the quality oil you're using doing its job. I'm betting/hoping it's just sludge that's been dissolved off the innards by the detergents in the oil. Do this mill have a persistent coolant loss?

Got the timing cover off and yes, there is a layer of sludge on everything. Not NEARLY as bad as the sludge in the oil pan, but it's definitely a thin layer there.
And yes, I did have a coolant leak. The water pump gaskets were leaking. I kept putting it off because it was such a small leak. I would have to add no more than a quart of coolant about every 3-4k miles. It was such a small leak it took me MONTHS to find it. No coolant actually dripped onto the ground.
Another thing I'm wondering about is slack in the timing chain. I have a good bit of slack in the chain (or at least I would consider it to be excessive slack). I can move the chain over with my finger almost 3/4 of an inch.

 

[Rocket Man]

Got the timing cover off and yes, there is a layer of sludge on everything. Not NEARLY as bad as the sludge in the oil pan, but it's definitely a thin layer there.
And yes, I did have a coolant leak. The water pump gaskets were leaking. I kept putting it off because it was such a small leak. I would have to add no more than a quart of coolant about every 3-4k miles. It was such a small leak it took me MONTHS to find it. No coolant actually dripped onto the ground.
Another thing I'm wondering about is slack in the timing chain. I have a good bit of slack in the chain (or at least I would consider it to be excessive slack). I can move the chain over with my finger almost 3/4 of an inch.

How many miles did you say that engine has on it? The NBS don’t have a tensioner on the timing chain so they do have slack. I put a new one on mine at 150k when I did the cam and I wanna say the original had probably 1/2” of deflection. New ones have about 1/4” IIRC. If you’re really high mileage it might be normal. Hopefully others will chime in, I’m going off an old mans memory which has been known to be faulty lol.

 

[mountie]

Back in the '70's.... I had a '70 GTO.... I replaced the timing chain every year!!

( back then it was easy to do anyway)

 

[ScottyBoy]

How many miles did you say that engine has on it? The NBS don’t have a tensioner on the timing chain so they do have slack. I put a new one on mine at 150k when I did the cam and I wanna say the original had probably 1/2” of deflection. New ones have about 1/4” IIRC. If you’re really high mileage it might be normal. Hopefully others will chime in, I’m going off an old mans memory which has been known to be faulty lol.

I'm at 160k miles. And yes it has just over 1/2" of side to side deflection, probably closer to 3/4".

 

[mountie]

Hows the sprockets ??
( I changed them also)