2000 Cadillac DeVille running rich city exhaust engine runs great uses boil it but doesn't burn have a blue oil leaves white smoke what could be the problem with it?

Yes this is correct, you can get important information from the colour of smoke from the exhaust:

Blue/Gray Smoke: Blue/gray exhaust smoke is an indication of oil burning in the combustion chamber. These are possible symptoms and causes:
Valve Seals: Leaking valve seals will cause blue/gray smoke at startup because oil leaks past the seals into the cylinder after the engine shuts down.
Valve Guides: Excessive clearance between the valve stem and the valve guide allows oil to leak past the gap into the cylinder.
Piston Rings: Worn or damaged piston rings will cause blow-by resulting in blue/gray smoke.
Worn Cylinder Walls: Worn cylinder walls cause blow-by resulting in blue/gray smoke.
PCV System: A stuck closed PCV valve will cause excessive crankcase pressure resulting in blue/gray smoke.
Black Smoke: Black exhaust smoke is an indication of a rich fuel condition. These are possible causes:
Fuel Injectors: A leaking or dripping fuel injector will cause a rich fuel condition.
Fuel Pressure Regulator: A stuck closed fuel pressure regulator will cause a rich fuel condition.
Fuel Return: A restricted fuel return line will cause a rich fuel condition.
White/Gray Smoke: White exhaust smoke is an indication that coolant is burning in the combustion chamber. These are possible causes:
Cylinder Head: A crack in the cylinder head (around the coolant jacket) will cause coolant to enter the combustion chamber.
Engine Block: A crack in the deck of an engine block near the coolant jacket will cause coolant to enter the combustion chamber.
Head Gasket: A damaged or blown head gasket will cause coolant to enter the combustion chamber resulting in white/gray smoke coming from the tailpipe.

What is a "level counter"? I am not familiar with this terminology.
What colour is the smoke from your tailpipe? White: possible coolant leak/head gasket failure. Blue: Possibly running too rich or burning oil. Black: Burning oil

blue smoke comes from too much oil in engine.thats can be the rings round the piston. the top ring is for leaving a film from oil so the piston
can run smoothly up and down.when its worn out you get to much oil
and see blue smoke.second possibility is valve setting,these tiny,
rubbers can worn out too and leave blue smoke behind.

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 !
What Your Exhaust Smoke Is Trying To Tell You

Stuck Open Fuel Injector how to fix

OK, check that the 2 fans are turning on when it gets to operating temperature. If not, replace the 3 or so relays that control the two speed fans on your car.If that doesn't solve the problem, then you may have to buy new fan motors and also have the harness replaced if necessary to make it cool reliably.

I had this problem on a 1997 Cadillac Deville Limousine that overheated over 157 deg. F and went into its limp mode for cooling the engine off by allowing 1/2 of the cylinders to circulate fresh air into the engine in case all antifreeze would leak out or the car would overheat.

Don't run the Northstar engine too long, more than 45 min. at a time in this limp mode.

Good luck on this repair of your Northstar Engine.

Hello white smoke is usually engine antifreeze,Blue smoke oil burning,Black smoke car running to rich on gas,gas is not burning properly.

Your cat won't cause your vehicle to smoke, unless there is oil on it, then as the exhaust warms up, the cat will burn off the oil. Chances are, there is something wrong with your engine.

There are a few diagnostic steps you can make to see if you're burning oil, running rich, or have a leaking head gasket:

Check your plugs. If they've got oil or a filmy, soot-like deposit, you've got worn valve guide seals or worn rings, and you're burning oil, or you're running rich, indicative of other problems.

The exhaust "smoke" that you see, if it's like a white/gray cloud, could be steam from a leaking head gasket or water in the intake. If it's blue-ish, that's normally running rich. If it's black, you're probably burning oil.

hi... it all depends on the colour of the smoke... usualy blueish smoke will mean it is oil burning and your piston rings may be getting worn if it is black then it might be running too rich etc.. a little bit of water is fine infact usualy it is a good sign that your engine is not running rich or lean so it is pointing towards oil seals... also if it was running rich it would probably do it more when it was cold

WHITE SMOKE IS BLOWN HEAD GASKET. BLUE SMOKE ENGINE BURNING OIL.DUE TO WORN PISTON RINGS AND WORN VALVE GUIDES.BLACK SMOKE EXCESSIVE RICH MIXTURE.CLOGGED AIR FILTER. FUEL PUMP PRESSURE TOO HIGH.SEVERE MISFIRE.LOW ENGINE COMPRESSION.

Rich fuel=black smoke.
Oil burning=blue smoke
Coolant burning=white smoke