No oil pressure on start up.

[donjetman]

We have variable displacement oil pumps, now we need variable minimum viscosity oil.

Oil pressure doesn't create shear strength. Viscosity doesn't = lubrication.

I'm no scientist, but I believe that if the oil were more water-like, such as 0W-20, it would require more volume and the resulting pressure to achieve the same shear strength. But, I run my stuff hard

@donjetman, have you noticed any change in your MPG since the lighter oil?

Before the oil reaches operating temp (200) our oil pumps spend a lot of time in bypass, what a waste. Engine oil is used for cooling. Oil volume will draw heat away.

I've noticed no changes in oil pressure or mpg since switching from 5w30or40 to 0w20.

over the yrs in this Denali I've run top shelf 5w40, 5w30, and now 0w20.

I don't hot rod our L92 6.2L.

In a perfect world (winning a lottery) I would stick a stock 4.8 w/VVT in our Yuk.

 

[iamdub]

Oil pressure doesn't create shear strength. Viscosity doesn't = lubrication.

Maybe shear strength isn't the term to describe what I'm thinking. I know viscosity doesn't equal lubrication. Lubrication isn't my concern- that's easy to get even with low pressure. Keeping a pressurized layer of oil between the moving parts is my goal. So, in my mind, pumping a high volume of a denser oil through those thin gaps (bearing clearances) creates a more solid cushion of oil to separate the parts.

Before the oil reaches operating temp (200) our oil pumps spend a lot of time in bypass, what a waste. Engine oil is used for cooling. Oil volume will draw heat away.

I've noticed no changes in oil pressure or mpg since switching from 5w30or40 to 0w20.

over the yrs in this Denali I've run top shelf 5w40, 5w30, and now 0w20.

I don't hot rod our L92 6.2L.

In a perfect world (winning a lottery) I would stick a stock 4.8 w/VVT in our Yuk.

Never thought about the cooling aspect of it.

Not hod rodding your 6.2 is why all this geeking out over oil viscosities isn't a concern for you and your engine will last a long time. My day is coming.

 

[avalonandl]

I'm in TX and I switched from 5W30 to 0W20 at my last oil change, (174k miles). I always do used oil analysis (UOA) so we'll see in 6 mths to a yr how my L92 6.2L likes it or not. Over at BITOG forum a smart fella did a thread about viscosity. Thinner oil, especially until the engine oil reaches full operating temperature (200*f), flows more volume thru the passages etc, which can be a good thing? We'll see?

The LT-1 and variations switched to that grade.

 

[donjetman]

@donjetman, have you noticed any change in your MPG since the lighter oil?

I believe I am getting a little better MPG now that I'm running 0w20 engine oil instead of 5w30 and 5w40.

When I fillup after doing my usual "local" driving the DIC indicates 420 mile range. It use to say 380 miles. I'm averaging about 19 mpg on the "hwy" now (driving the speed limits) between our 2 homes which are 1k miles apart. I've done that leg 3 times this summer averaging 18.4, 19.3, and 18.7 mpg.

Soon I'll do a 4th hwy leg and will have 6k miles on this load of 0w20 oil. I plan to send in a sample to a lab for UOA (used oil analysis).

 

[Dustin Jackson]

I believe I am getting a little better MPG now that I'm running 0w20 engine oil instead of 5w30 and 5w40.

When I fillup after doing my usual "local" driving the DIC indicates 420 mile range. It use to say 380 miles. I'm averaging about 19 mpg on the "hwy" now (driving the speed limits) between our 2 homes which are 1k miles apart. I've done that leg 3 times this summer averaging 18.4, 19.3, and 18.7 mpg.

Soon I'll do a 4th hwy leg and will have 6k miles on this load of 0w20 oil. I plan to send in a sample to a lab for UOA (used oil analysis).

@donjetman Hold on, you are using 0w20 in a 6.2? Can you tell me more about why you did this, How long you've been running it, and your results?

 

[donjetman]

@donjetman Hold on, you are using 0w20 in a 6.2? Can you tell me more about why you did this, How long you've been running it, and your results?

Yes, I put Amsoil 0w-20 in it for the first time 5500 miles ago in March this yr. Vehicle has almost 180k miles on it now. In a week or 2 I'll have 6500 miles on the oil, and I'll send in a sample for analysis and I'll post the results here at TYE. It could be eatin itself alive. This next analysis will tell the tale. It will be the 6th that I've done on this vehicle.

I spend too much time on Bobistheoilguy forum. I've been convinced (for now) that thinner oil will flow more volume, thus cooling and lubricating better. I always drive whatever the speed limit is, don't tow, and never hot rod it. I wish it had a 4.8L w/VVT.

We bought it used w/130k miles Nov of 2018 no mx records. It had issues. FIXES: I immediately replaced the rear main seal, installed the updated valve cover, did a piston and combustion chanber soak which freed up the stuck oil rings. All 8 cylinders had stuck oil rings. Since then (4yrs and 50k miles) it never needs any make-up oil between the long oil change intervals that I do.

Mods I've done are: 1) engine oil bypass filter system; 2) small engine oil cooler; 3) 10.5 qt oil sump capacity; 4) 180* thermostat

 

[Dustin Jackson]

@donjetman I look forward to the oil analysis results!

Curious about the stuck oil rings, how did you determine they were stuck and what was the process you used to unstick them?

 

[donjetman]

The PVC system is built into the valve cover. The PO didn't change the original valve cover out for the new improved valve cover. As a result the engine was sucking a lot of oil from/thru the bad valve cover pvc hose and into the intake manifold and into each cylinder.

It was consuming and leaking 2 oz per 100 miles. The rear valence panel on the passenger side (exhaust pipe side) was covered in exhaust residue. All the spark plugs looked like the one below. And I discovered a GM TSB about oil consumption: https://f01.justanswer.com/ebrock63...il+Consumption,+MIL+ON,+Engine+Runs+Rough.pdf
Not exactly like the TSB describes, I squirted Gunk brand "Motor Medic" in each spark plug hole and let it soak for a couple of days, occasionally moving the crankshaft back and forth with a socket/breaker bar on the harmonic balancer bolt, then replenishing each cylinder with the Motor Medic.

Old & new improved vc pic below