Q: Tailpipe smoke

For quite some time I've had noticeable tailpipe smoke. Only after its been idling(at a stop sign or more so at a red light); only when I initially step on the gas then it dissipates ; I get a trail of smoke behind the car, well at least used to-now it's a cloud puff! Overall the car is still running rather well... it doesn't overheat; although a small (oil leak? Which it's had since I bought it several yrs ago) no excessive fluid loss of any kind; it doesn't have quite as much power/speed going up a hill as it used to; no delay in power driving around town, excellent on the high way; while driving if you didn't notice the cloud in the rearview mirror you wouldn't think anything was wrong with the car...?

My car has 196,000 miles.
My car has an automatic transmission.