Vortec 5.7l oil consumption.

[Supercharged111]

Because the "thinner than water" oil viscosity burns quicker and hastens oil consumption.

There's nothing thin about a 40W. It's a 0W at 32 degrees and a 40W at 212 degrees. When a synthetic oil breaks down, it reverts to the higher number, not the lower. I doubt at 5,000 miles per change that that's a significant factor. A 0W is still multiple times thicker at 32 than a 40W is at operating temperature so the thin oil argument is moot.

 

[badco]

Newer 5.7s like the vortecs have a thin 3mm oil ring pack and are unable to handle to thick oil. My old sbc stuff id run a 20/50 with no trouble but not my vortec. 10-30 or 10-40.

When I tried to run synthetic 5-30 in my 350k+ vortec it started leaking out rear seal and burning a qt or more between oil changes. Went back to a conventional 10-30 and oil consumption went away.
Honestly feel that the rings and depth of hone are to worn for the synthetic.

Never used the profilometer on the high milage cylinders to confirm it mainly cause it still running

 

[Nad_Yvalhosert]

There's nothing thin about a 40W. It's a 0W at 32 degrees and a 40W at 212 degrees. When a synthetic oil breaks down, it reverts to the higher number, not the lower. I doubt at 5,000 miles per change that that's a significant factor. A 0W is still multiple times thicker at 32 than a 40W is at operating temperature so the thin oil argument is moot.

No you're right. 40 weight is 40 weight. But it's the cold number that is crutial in my example
The oil is being consumed at cold operation, at cold start. When loose tolerances allow thin oil to bypass the piston oil ring, and past shrunken valve stem seals.
When the engine warms up, and metal expands, and seals expand, oil consumption slows.
You never seen (on other vehicles) blue exhaust at startup? Blue is burning oil...
Here in the northeast where we have 100 degree swing in temps from winter to summer, my engines see extremes, therefore benefit from relativly thick, 10w40 oil year round. If your climate is more temperate, perhaps you can get away with a different viscosity not specified by the manufacturer.

All I'm saying is, based on my experience, thick oil is more desirable for my uses, and burns less in my vehicles, based on my use of my vehicle.

 

[Supercharged111]

I'm more concerned with oil flow when it's cold because it's so much thicker then no matter how much of a split there is. Also, per someone else's post, the large split is more stable with a synthetic than a dino oil so no worries about wherever it reverts to. I've been using synthetic so long I'm not sure how much it burns compared to dino. I did it so I could extend my intervals, i.e. less work.

 

[Nad_Yvalhosert]

I'm more concerned with oil flow when it's cold because it's so much thicker then no matter how much of a split there is. Also, per someone else's post, the large split is more stable with a synthetic than a dino oil so no worries about wherever it reverts to. I've been using synthetic so long I'm not sure how much it burns compared to dino. I did it so I could extend my intervals, i.e. less work.

Starting with 10 weight cold, 8 hours later isnt a problem when the previous drive cycle hot 40 weight hasn't fully drained back. Meaning I've never experienced a single issue driving to work, letting it sit in the parking lot, then driving home. Same as driving it home, letting it sit overnight and firing it up to go back to work.
Perhaps it might be different if one was to let the truck sit a month due to losing a job due to Wuhan Flu, then firing it up and driving it like you stole it...

 

[Nad_Yvalhosert]

Besides what truly is the cold viscosity difference in 5/30 and 10/30? In real world numbers...

 

[Nad_Yvalhosert]

There's nothing thin about a 40W. It's a 0W at 32 degrees and a 40W at 212 degrees. When a synthetic oil breaks down, it reverts to the higher number, not the lower. I doubt at 5,000 miles per change that that's a significant factor. A 0W is still multiple times thicker at 32 than a 40W is at operating temperature so the thin oil argument is moot.

I thought synthetic oil was designed NOT to break down. That was the whole premise of synthetic...

 

[badco]

The only rings that really matter are the top for compression and the oil ring. Second is just a wiper. High mileage and ring wear itself isnt the big issue, its the depth of the crosshatch in the cylinder that controls most of the oil consumption

 

[Supercharged111]

I thought synthetic oil was designed NOT to break down. That was the whole premise of synthetic...

It takes more to break it down, yes.

 

[noabarron3]

Define "degrade".

My Trailblazer goes about 13,000 miles (because that's when the Oil Life Monitor shows it needs to be changed), gets a fresh filter and oil topped-off. Then it goes another 13,000 miles before I dump the oil and change the filter again. Oil samples taken at 26,000 miles show oil is still fit for use. but I can't bring myself to go another 13,000 miles. I only have 250,000 miles on the vehicle, so I don't know how this is going to work out long-term, but "so far, so good" aside from the increase in oil consumption noted in my previous post.

Feedback fuel injection and overdrive transmissions have made major improvements in the service life of oil.

Degrade means degrade. Glad I could help.