Antifreeze in oil

Generally, Which system had the most pressure when the leak occurred? If the oil system had the most pressure, at that time, then it makes sense that you could get oil in the cooling system with no antifreeze in the oil. Or vise-versa.
There may be other variables? Just my 2 cents.

Chevy has a problem with this . The check gauges light means its the oil or the anitfreeze . I don't know what year your vehicle is but the basic problem is the intake manifold is aluminum and the block is iron they expend and contract at differant rates so if the engine gets to hot the gasket that seals the two fails because there isn't enogh bolts holding the intake down to the block 8 total and all in the 4 corners of the block - maniflod . The problem is vary likely the intake manifold gasket check for oil in the antifreeze and antifreeze in the oil on the dip stick it will look like a white fomey residue on the stick and in the antifreeze if you take the radiator cap off you will see oil floating on the top . You can save the engine but the intake manifold gasket needs to be replaced . The olny other cause would be the engine oil being to low but in this case the engine is probably on the way out depending on what engine and what year

Check you oil for signs of coolant contamination. If coolant is present in the oil, you may have a leaking head gasket or intake manifold gasket. If there is no sign of coolant in the oil, the antifreeze could be leaking past the intake gaskets and into the combustion chamber. It could also be a leak that only shows up when the engine is running, and you are losing the coolant as you drive. This kind of leak is very difficult to locate. You will have to look for signs of antifreeze around the upper and lower intake gasket area with a strong flashlight. Also check for signs of leakage at the upper and lower radiator hose connections and the drain valve at the bottom of the radiator. If you smell antifreeze inside the car, check the carpet for dampness caused by a heater core leak. Sounds like a lot of work, but these mystery leaks as I like to call them, can take repeated inspections before you finally locate them. I hope I have been of some help. Good luck and let me know what you find.

If you have the V-8 Engine, just totally disregard this post.

If you have the 3.8L V-6 engine, your oil consumption problem is most likely to be caused by the PCV Valve if you cannot find any external leaks. These are also known for the upper intake plenum leaking antifreeze. The ports in the manifold that go to the throttle body are made of very thin plastic. The EGR tube, with its hot exhaust gasses, goes right between them. This causes the plastic to heat up and crack, causing an antifreeze leak that goes directly into the intake and gets burned in the combustion chambers.

DORMAN makes a replacement upper plenum kit to fix this problem. The kit includes the upper plenum with thicker coolant passage walls, an intake manifold gasket set, a smaller-diameter EGR orifice, and a new PCV Valve. This kit will probably fix BOTH of your problems.

The DORMAN part number for your car is 615-180 Shop around...prices vary considerably.

Late model GM cars are plagued with antifreeze leaks around the Upper Air Plenum gasket and also the Lower Intake Manifold gasket. This is brought on by Dex-cool antifreeze deteriorating the gasket materials. If the Lower Intake gasket is leaking, it may have contaminated your loil with antifreeze. If there is antifreeze in the oil it should show up on the dipstick as a gummy sludge. GM has issued Technical Service Bulletins to their dealerships concerning this issue. Check with your local dealership to see if they will repair it at no charge. There currently is no recall, so they probably won't. In that case, take it to a good garage and have it repaired. Don't wait too long. If the oil is contaminated, it will damage your engine from lack of lubrication.

You either have a cracked cylinder head or a leaking cylinder head gasket.

I see a lot of lower intake gasket leaks on these but usually you get an external leak or you'll find coolant mixed with the oil, not a misfire. Upper plenum is dry on the 3.1 and just bolts onto the top of the lower intake. We usually apply pressure to the cooling system overnight with the spark plug removed from the misfiring cylinder. If there is coolant in the cylinder come morning then you only have to figure out where it is coming from. If the plenum is removed during the test you might be able to see where the coolant is or isn't coming from with a borescope by looking down the intake runner.

itr could be or it cold just be little blow by, i would just clean it up and replace the pcv valve

Get that fixed ASAP, Water in the oil will destroy the bearings. The intake manifold gaskets may be bad, leaking water into the engine. Have a repair shop check it out and recommend repairs. Do not put this off, unless you want a new car.

Blowing out the exhaust. Look for white smoke.