Have you tried valvoline maxlife 10w/40 its a semisynthetic, they also do a fully synthetic one but that 5w/30...
i've use this stuff for years in my gti's and even my vr6 is using it but i alternate it between normal semi oils at every oil change so that it doesnt over do the seals..
and my gti did 211,000 miles on the orignal engine which i drove hard everytime i drove it... the engine was still ok when i had to scrap it due to the gearbox!!
basicly alls the oil does is it conditions seals and stops leaks, i thought that you may benifit from using such oil as i know the cam cover gaskets are prone to leaking and are exspensive to have done, ie engine out $$$ in labour charges.. where as a couple of maxlife at your next oil change may well do the trick, also if yours is hitting 100,000 miles and has a few blue puffs of smoke out the tail pipe on hard drives that may also stop....
www.valvoline.com www.mobil1.comits worth trying the max life oil out, and please get back to me if it works!! i'd love to know if it fixes your oil leak...