Smoke
Before the members start yelling out to use the search option, there are different reasons for white smoke from the tailpipe.
1.) Blown Head Gasket (BHG): very serious problem, and it smokes thickly from the tailpipes at all times, milky radiator fluid, and constant overheating.
2.) Dirty PCV Valve where carbon deposits gunk up the valve and the smoke comes and goes intermittently.
3.) Wet Gasket Seal, which usually only smokes after the long idles
The bottom two are the most common problems and not as serious as the BHG.