I bought this 2001 Buick LeSabre Limited about a month and a half ago. When I bought it the previous owner said it was using coolant and oil. I changed the LIM gaskets(updated design) and upper intake plenum. While I had everything apart I cleaned the throttle body very well. I don't think that they changed the oil too often as I found sludge when I changed the front valve cover gasket. I ran a hanger wire down the oil return holes to ensure they were clear. The coolant level is staying constant but it still seems to be using too much oil. It doesn't burn it constantly but only after about a half hour of driving. By that time I am in stop and go traffic in Brooklyn and it always blows a cloud of blue smoke when I take off from a stoplight. It will only do it if I have been idling for more than 10 seconds so it doesn't do it from just a brief stop at a stop sign. I have changed spark plugs(it seemed like the originals were in there as the nuts were rusty and they were AC Delco) with NGK TR55. The original plugs showed no signs of fouling. The engine has 139k on it and is very reliable, has decent power and gets good gas mileage but this smoking is embarrassing...Any ideas on what could be causing this???

Sounds like a compression test is in order, with the infrequent oil changes and who knows how long coolant has been in the oil I would suspect the piston rings or perhaps scouring of the cylinder walls. Although I've never heard of any valve guide problems in the 3800 that'* often the source of oil consumption in some engines.

2004 Bonne SLE
1971 Chevelle SS

get a leak down tester you use with a good air compressor if leak down is say less then 15% rings are good
first start of he day with smoke is a sign 90% of the time valve seals or guides worn
as oil leaked past any open valves when you turned the motor off

There are metal rings around your valve stem seals....if broken, they will cause the seals to leak and you will burn oil.....you will have to remove BOTH valve covers and inspect these seals....you may find the broken rings lying in the in the top of the head....

It doesn't smoke on startup only after about 1/2 hour of running.

What type of oil are you using? I suggest to change it to mineral base and see what happen.

Why mineral base?

You all so might want to check the PVC valve to make sure its not clogged that could make to much crank case pressure and cause all kinds of problems
Is it doing anything like puffing fumes out with the oil cap off after 30 mins of driving?
The only thing is I would have new seals that go around the PVC valve and the cap
that'* on top of it before you check it
and use some oil on the seals putting it back together

PCV is new. It came with the Dorman UIM.

When I run the air conditioning it doesn't smoke. I also had a P0442 code come back a few days ago....I cleared it and have no other codes(It passed emissions inspection last week).