intermitent knock noise

[Mick]

Hey i have had an intermitent loud knock noise from my engine and it seems to run a little noisy, the car hadnt been started for about a month and for most of this time the plenum and a cam cover was off, but i had gladwrap covering exposed areas. Now i remember quite a while ago now when i polished the cam covers and put them back i noticed it ran noisy (ticking noise). The knock noise i beleive came from when the detanated some time ago (Sounds like it coming from the turbo

).

Now im wondering if changing the engine oil would be qa good idea. Because the cam covers have been off couldnt the oil have gone a little tacky and maybe making the valves/lifters stick a little.

Also what oil should i use, its a rbr2det, i can get fuchs 0w20 cheap, would this be good to use ?

Anyways any help would be apreciated ..