Several months ago I checked my oil level and it was full. Since then about 1-2k it was driven. Today I checked the oil and it was a showing 3/4 full. Also when I turned on the car this morning alot of white smoke came out from the exhaust. I also noticed dried oil on the garage floor where the car is parked. Am I hit with a double whammy? I've been reading online that every few thousand miles cars burn approximately 1 quart of oil, but this has never happened to my car, it has always stayed at the full mark. I also checked the oil level in my garage (flat surface) and after it was just driven (hot). I also use Mobile 1 synthetic oil.

 

Before I rebuilt my engine it was burning a quart about every 1k miles. If you want to track down an oil leak you could buy a oil dye and see where it is leaking from.

 

If the car oil level gets low will the engine oil light turn on? If so how does it detect low oil level? My car is a 2005 TL.

 

External oil leaks are 1000x easier to fix than if you were burning oil and you need to rebuild the engine, regardless where it's leaking from.
Find and repair the leaks first and foremost. If your oil level is still dropping after that, you could try switching to one grade thicker oil, see if it helps the oil consumption.
The engine doesn't have an oil level sensor. If the oil gets too low, your oil PRESSURE light will come on, which when that turns on, is almost too late.

White smoke is usually burning coolant. Sounds like you should also be checking your coolant levels too. Luckily checking for coolant leaks is a bit easier because you rent a coolant pressure tester from Autozone and watch for bubbling/leaking coolant.

 

Is it cold where you are? There could have been a lot of moisture in the exhaust causing white smoke on startup or lots of ethanol at the bottom of your tank being sucked up on first start.

Where do you see the dried oil? Oil filter housing is common and easy fix esp with age/higher miles.

 

It's about 35F here. I saw the dried oil on my garage floor. I was a bit puzzled, I thought oil wouldn't dry.

 

White smoke = coolant and/or condensation. Blue smoke = oil.

Couple thousand miles in several months isn't a lot. Are you short-tripping the car a lot?

The car should tell you when it's low on oil... but remember the dipstick never lies.