Engine oil leaks not only increase engine friction, but those underhood leaks (particularly at the valve covers) allow oil to seep onto hoses, belts and wiring harnesses, causing them to deteriorate. Periodically tighten the screws holding all oil-sealing covers, like cam or pushrod gallery covers. If a washer is the specially shaped load-spreading type and it's missing, get a replacement that matches the original, as it significantly improves sealing over an ordinary washer.

Some OEM-type gaskets have been superceded by a newer style because the originals were -you guessed it- prone to leak. So be sure you're buying the newest revision. Also check the oil pressure sending unit for seepage, and if necessary, remove the unit and wrap the threads with Teflon tape for a better seal.