oil leak on 1997 Mitsubishi Mirage

Have oil seepage only when engine is hot after running for about 1/2 hour will find drop on oil pan at the drain plug top of oil filter valve cover gasket needs replacement tightend down bolts on valve cover oil drop got smaller.Car has 175,500

Asked by for the 1997 Mitsubishi Mirage
To pin point where oil is leaking from the engine may need to steam clean the engine first. Starting with a clean engine and then running the engine it may be easier to identify specific leaks. If the oil leak can not be identified, florescent dye may need to be added to the oil and the engine run for a while. After running the engine the dye used has florescence in the dye is visable under UV light and it helps pin points the source of the leak. Identify the color of the oil to differentiate wether the oil leak is steering fluid, brake fluid, or transmission fluid and try to identify the location of the fluid leak under the vehicle, ie front of engine compartment, rear of engine compartment , passenger or driver's side of vehicle. Oil leaks may be caused by a partially plugged Positive Crankcase Valve (PCV valve). This system is an emission control device that allows the engine to breath, if it gets plugged crankcase pressure builds up and causes the engine to leak oil from various gaskets and seals.
Thanks for your help I took it back to the oil changing place and told them about the problem after I replaced the valve cover gasket.The owner was down below for about 3+ minutes only to tell me that I have small seepage at the oil pan gasket.He also told me that the rack& pinion is leaking as I saw thick grease as far back as 18-24" from the rack& pinion boot ,how can this be if their is no rips or tears in the boot itself.