tappet issues

A couple of oil related questions.Firstly its time for 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

The tappets are mechanical as opposed to hydraulic so an oil change wouldn't make any difference, and they would also be noisy from the second you start it too, not just from 2k rpm as you've said. Could be the vacuum pump, I wouldn't want to try diagnose on here. But it's not the tappets at fault, I can tell you that much. Mine has done similar mileage and I used 15w/40 Morris Turbo Diesel Oil in it on the last change.