Thick oil, blue smoke from exhaust

Check engine compression. It is possible for water to be leaking into a cylinder and not be leaking into the oil.

The most common cause of blue exhaust smoke is oil leaking past engine seals and into the cylinders where it then mixes and burns with the fuel. This is most frequently seen in older or high mileage cars with worn seals and gaskets. It only requires a very small amount of oil leaking into the cylinders to cause excessive blue exhaust smoke.

Blue exhaust smoke only at start-up can indicate worn piston seals or damaged or worn valve guides which may also cause a rattling noise. An external engine oil leak can drip onto hot engine and exhaust parts causing what appears to be blue exhaust smoke. Other possible causes of blue exhaust smoke include: piston wear, worn valve seals, a dirty or non-functioning PCV valve, worn piston rings, an intake manifold gasket leak, worn engine oil seals and possibly even head gasket failure.

Oil leaking into the cylinders can cause a rough idle, misfire and fouled spark plugs. In addition, a reduction in power and oil loss can be indicators that the blue exhaust smoke is caused by an internal engine oil leak. Internal engine oil leaks can also allow fuel to mix with the oil in the crankcase which will degrade the oil and prevent it from adequately protecting the engine.

Operating a car with a severely dirty oil filter, air filter or improperly functioning PCV valve can also sometimes result in engine oil blow-by, oil loss and blue exhaust smoke. Periodically checking the engine oil level with the oil dip stick will indicate if there is excessive oil consumption. Higher viscosity engine oil can sometimes temporarily reduce the amount of blow-by; however, this is not generally recommended. Excessive blue exhaust smoke indicates a possible internal engine oil leak that should be inspected by an ASE certified mechanic.

If it's blue smoke, your burning oil. Get the head gasket checked. If that's ok your looking at something more serious, (more expensive), inside the engine.

What color smoke ? Blue = oil burning , black = too much fuel (rich) white = coolant - blown head gasket ,cracked head or block . White also could be caused fuel running through the engine , no combustion !
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A V8 engine will start to consume more oil as they get more and more
miles on them. The valve stem seals and piston rings wear, and let
more and more oil burn off in the exhaust. How many miles are you
travelling in said 3 weeks?

Blue smoke is never a good thing....

Blue smoke is caused by engine oil entering the cylinder area and being burned along with the fuel air mixture. As with the white smoke, just a small drop of oil leaking into the cylinder can produce blue smoke out the tailpipe. Blue smoke is more likely in older or higher mileage vehicles than newer cars with fewer miles.
How did the engine oil get inside the cylinder in the first place? The car has many seals, gaskets, and O-rings that are designed to keep the engine oil from entering the cylinder, and one of them has failed. If too much oil leaks into the cylinder and fouls the spark plug, it will cause a misfire (engine miss) in that cylinder, and the spark plug will have to be replaced or cleaned of the oil. Using thicker weight engine oil or an oil additive designed to reduce oil leaks might help reduce the amount of oil leaking into the cylinder.

your engine has worn valve guides, piston rings An engine that burns a lot of oil (more than a quart in 500 miles) is an engine that needs to be overhauled. Normal oil consumption should be a quart or less in 1500 miles. Most newer engines consume less than half a quart of oil between oil changes (every 3000 miles). So if your engine is burning oil, it's essentially worn out and needs to be repaired.
Because the cost of overhauling or replacing an engine often exceeds the value of an older car or truck, many people will just keep on driving a "mosquito fogger" in spite of the blue clouds of smoke it leaves behind. Never mind the pollution it causes, oil is cheaper than a new or rebuilt engine they reason. That philosophy may be okay if you live out in the sticks somewhere. But in urban areas that require periodic vehicle emissions testing, an engine that's burning oil usually won't pass the test because of excessive hydrocarbon (HC) emissions. You may get by on a waiver after you've spent some money (in vain) on a tune-up, but the fact remains you're still a polluter.
An engine that burns a lot of oil will also eventually foul the spark plugs. Thick, black oily deposits build up on the plugs until they cease to fire. Then the engine misfires and loses power. Cleaning or changing the plugs may temporarily solve the problem, but sooner or later they'll foul out again.
Forget about "miracle" oil additives or pills that claim to stop oil burning. They don't. Better to save your money and put it towards a valve job and new set of rings.

Sounds to me like they did a bad head job. No pun intended. lol, White smoke indicates moisture in exhaust but black smoke indicates a oil leak. I would take it back and have them check the job they did. If the car is over heating then the head gaskets are pretty much blown.

IS the smoking extremly heavy ? Extreme heavy smoke where you cant see behind the car would indicate turbo. If this is the case no engine damage should have occured. The turbo on these cars are oil and water cooled, The heavy smoke indicates a worn seal in the turbocharger is leaking oil directly into the exhaust system and burning there. Catylitic and oxygen sensor damage may occur but engine damage is unlikely.

If you have steady thick white smoke and it smells like anti freeze it is most likely the head gasket. The head gasket can fail in different areas. If it has white smoke it failed between a coolant passage and the combustion chamber. If the oil is milky it failed between the coolant passage and an oil passage. Just because the oil isn't milky doesn't necessarily mean that the head gasket it's blown.

White smoke from exhaust = water into the cylinders, when this happens it usually means head gasket gone or starting to go.
Check the water level, and take the car to the garage for a check up , if it is the head gasket, as I think, you risk to blow the engine at any time.