Without getting into a discussion relating to the merits (or not) of the LS3 intake box and why GM put an addition there, the bigger question would be why install an oil catch can.

For the purists who feel the GM design is perfect, then they change nothing. However, GM must meet a large number of government rules and regulations that extend far beyond what is commonly known. Many of those requirements are not necessarily beneficial to the auto enthusiast, which is why the aftermarket exists. The aftermarket will fill a need, either real or perceived (aka created), to make a profit.

Mods tend to be either appearance or performance related and many people buy the performance stuff just for the appearance of performance. It's why the Corvette is so popular and the GS in particular.

Now about the catch cans. Is it appearance or performance?
The engine lubrication system is pretty much sealed from the atmosphere, with the only access through the air filter and exhaust tips. Catch cans are located in the line between the lower engine (below pistons) and upper engine (above pistons) and trap oil through filters and cooling (condensation) of the hot oil vapors. Without a catch can, the oil laden vapors continue uninhibited to the intake manifold and are burned along with the air/fuel mixture. While it's true that some oil will condense and puddle in the intake manifold, it also continuously evaporates and is burned. It's not like you have raw liquid oil going into the combustion chamber or dripping out onto the air filter.

You have to ask yourself how much oil you burn off the cylinder walls between oil changes, assuming your catch can was 100% efficient and compare that to the amount of oil caught in the catch can.
Let's create a simple scenario of oil usage. Consider an average 25 MPG and 8,000 mile oil changes. At the time of an oil change, the level was down 1/2 quart and you emptied 4 oz twice from a catch can, then you burned 8 oz and poured out 8 oz for a total of 16 oz during the 8,000 miles. Without the catch can you would have burned all 16 oz along with 320 gallons of gas, which equals an oil to fuel ratio of 1:2560 compared to a 1:5120 ratio using a catch can. Neither you nor GM can measure the performance difference and that's why GM didn't put one on the car.

It all comes down to a perceived problem created by the aftermarket to sell an unneeded product to uninformed buyers. If you think it looks cool and don't mind the expense or the hassle of regular draining then by all means, add one. It'll match the chrome liquid caps in appearance and performance.

 

Sorry for throwing more Catch Can stuff into this thread, but I feel that it somewhat answers the question posted earlier.
My catch can set up is catching oil (On my 2013 GS)
'Need' ...? I installed a catch can on my GS & it is definitely catching some oil. The engine would most likely still be running if it didn't have one...But...It does catch oil. Oil that would have gone back into the intake... I would say, installed correctly, Catch Cans are really beneficial for an LS engine. I have a catch can thread I started awhile back. (https://www.corvetteforum.com/forums...h-can-pic.html) Dano523 was a big contributor to the thread & is a wealth of knowledge on the subject of Catch Cans.

 

adSome high end cars have a system like the 'catch can' installed from the factory. I'm thinking one is the Mercedes. I read about it on the internet to long ago to remember which cars have that system!

 

NSF, for my CC usage experience, I find I catch more oil in Daily Driver use than during track sessions, suggesting there is more oil blow-by when the engine is cold than when it is hot. The CC helps to keep oil from accumulating in the intake and it also helps cut down on engine deposits because motor oil doesn't burn as cleanly as gasoline.

Spinmonster removed some heads and compared CC equipped engines v.s. non CC'd engines. There was a visible difference between them.

Personally, I try to keep my engine as clean as possible, I always use Chevron or Shell gasoline and I use the CC to also cut down on deposits.

 

Not trying to be a Negative Nancy here, but just offering up some things to think about.

Adding oil to gasoline actually increases, not decreases, the octane rating.
Ethanol raises the octane rating too.
Increasing the octane alone, won't make an engine produce more power.
Higher octane fuel will allow advanced timing and higher compression, which results in more power.
Octane enhancers (real ones) require about 1 oz/gal to raise it 3 numbers.
The average 2-cycle engine runs on a 40:1 gas to oil mixture.
Once a 2-cycle engine warms up, the gas vaporizes and most of the remaining oil is for lubrication.
The oil burned in a 4-cycle engine is primarily that which is washed off the intake valve.
One of the problems with direct injected engines, is there is no fuel to wash the oil from the intake valve.
Assuming your 25 MPG car uses 1/2 quart of oil between 8,000 mile oil changes, that's a 2,500:1 gas to oil ratio.
If you use an oil catch can, your approximate gas to oil ratio is 5,000:1.
A 5,000:1 ratio is one ounce in 39 gallons.
PCV systems have been on nearly every car built since the mid-60's and pulling oil through the intake manifold.