Firstly, you have to point out the leakage point. After that simply, repair or replace in case of much severe issue.
oil leakage
Oil leakage and loss of compression and power loss.
Slightly possible, not likely.
Internal oil consumption. External oil leakage from seals and gaskets.
check your pvc. If that is not working your engine will blow the oil out somewhere.
best is 20w40 grade engine oil.
It is always best to use the oil recommended by your vehicle manufacture. If you are considering the difference between Synthetic oil and Conventional (pumped from the ground); if your owner's manual says to use synthetic, you need to use synthetic. But if your engine was designed around conventional, then you can upgrade to synthetic. Synthetic has advantages as being better at cleaning and protection your engine, but if you have a higher mileage vehicle, synthetic can cause leakage of the gaskets and oil seals.
Over pressure in the engine results in problems, e.g. oil leakage, over pressure in the engine will cause the pressure to leak through the seals for example oil filler cap and cylinder head cover, at the same time causing engine oil loss.
Should have a drain plug either at bottom of engine or at lower end of oil reservoir
Draining the excess will solve the problem.
The fly wheel/drive plate. the rear main bearing seal is mounted at the end of the engine block, which prevents oil leakage from the engine block.
best oil is 5w30