I just added 2 quarts of oil to my 1990 Nissan 240SX because I was under the impression that the oil was low. Now every so often when I drive, light colored smoke is emitted. Is this excess oil burning off and will resolve by itself?

 

It's possible that the smoke is excess oil burning, but that's not your main problem. Find your oil dipstick and read the oil level. If it is over the full mark, then drain some oil to bring the level down to the full mark. Having too much oil can cause mechanical problems in the engine.

On the other hand, if the smoke is coming from under the hood instead of out the exhaust, then you probably spilled a little oil on a part of the engine that gets hot and the oil is just evaporating. This will stop eventually. It may leave a slight oil coating on your windows you'd want to wash off.

 

Change the oil and filter, putting it back to the proper level.

Change the PCV valve and inspect the system for clogs and broken parts.

If the smoke coming out of the tailpipe is blue, it burns oil. Engine's on borrowed time. If it leaks from under the hood, it could be a bad valve cover gasket, leaky oil pressure switch, etc, etc.