Oil question

A couple of oil related questions.Firstly its time fo an oil change as i got to replace the 2 oil cooler pipes so might as well do it at the same time.Is the manufacture spec oil still ok for an engine with 140k on it or should i go a little thicker as i suspect the tappets are starting to rattle a little though this may go with fresh oil, which leads on to my second question.Looking around past posts i am wondering if it is the tappets or could it be the vaccuum pump as i have seen several post regarding this. The ticking noise starts around 2k rpm but i am thinking its too slow a noise for tappets.Is there an easy way to check the vac pump.Cheers

i run 15/40 from millers oils.
check valve clearances while your in there.
re vac pump, with engine off, press brake pedal. start engine. should feel pedal drop an inch or two. proves its working, but would need to remove it to diagnose if its the cause of yer rattle.