2003 cadillac cts v6 3.2 liter. white smoke

How does what read ? What fuse for the A/C ?

Consider purchasing warranted rebuilt cylinder heads from "Cylinder Heads International" for $275.00 each with free return shipping of your cores. If you choose to do the work yourself get a library card which will allow you to free online access to Haynes or Chilton's repair manuals. Or for $27.00 get a one year subscription to "All Data" which has expanded information. Any of the above will have the timing spec's. Don't make the mistake I made trying to do it without borrowing or buying the tool for that purpose.

Too big a job for an answer here. Best to buy a service manual if you want to try to do the job yourself

It could be doing its job, sounds like what you put in tank is problem. Oil change would not cause that. I would not worry unless it keeps going after fuels runs down.

it will byitself just drive it a bit. the valve cover seals or plug tubes need replacing

change the air filter for air conditioner

Check the valve covers, oil pump or head gaskets. Just because there is no water in the oil, doesnt have anything to do with a oil leak, unless you are noticing white or blue smoke out of the exhaust

Regular 5W30 oil will work just fine in the '03 CTS. Your owners manual will tell you to stay away from any other viscosity (5W20, 10W30, etc) because they will be either too thick or too thin. It does not require synthetic as it is equipped with a 3.2 liter engine that was more or less derived from the Catera, but just didn't break as much. They only ran that engine for a year and started using the 3.6 liter VVT (variable valve timing) which does require synthetic oil (5W30 Mobil 1).

If the AC compressor was working full time including when the heat was on in the winter, this would certainly cut short the life span of the compressor. Usually, the compressor won't come on unless climate control is calling for AC. If this was the case, the issue is more likely the climate control itself, either a sensor or the whole unit. Should have been caught when you had it diagnosed in the winter if this was when you had it in the shop. Hope this answers your question. Best of luck.
Greg

I concur with emissionswiz; it sounds like a typical sign of a leaking of 'blown' head gasket and the white smoke could well be coolant+water.