i own a mk5 astra 1.9cdti 150 i have owned it since new from 2005 with 23000 miles on the clock,the warranty has expired,so i thought i might as well get it serviced from my friend who works at the vauxhall dealers by day and he does foreigners on the side of which he uses genuine vaux dealer parts and so i save myself money,the question is that he recommends and uses gm 10-40 semi synthetic oil for my diesel engine, is that a good engine oil? do you think it is the right oil?should i have it changed for a fully synthetic oil like castrol edge or mobil one synthetic?????? i am confused at the moment as to get it changed for fully synthetic or leave that semi synthetic gm 10-40oil.
i would like to hear your views so if you could leave your comments and i shall listen to all your replys and act accordingly. thanks!!!