nervous twitch type aversion to manufacturer's ownbrand oil - costs a bomb and comes from who knows where.
If a 70k can run on 0W40 with no leaks and not using any that I will stick with that, why put thicker than necessary in? Only slows the turn-over, causes more friction, worsens economy ...
Thanks for the help though.
GM's own semi synth oil is some of the cheapest I know on tradeclub (less than £10 per 5l can). At that price, I'll happily change it every 3k or so (about when it changes from clear to light brown, ie if I can see the oil on the dipstick, its due for change!), which will do the engine a whole heap more good that a fully synth oil changed every 10k

Added to that, GM oil is a quality oil supplied by Fuchs.
For the past 70k miles (ie, in my ownership), my MV6 has had this 3k oil change, and it's probably the sweetest Omega engine I have driven (and I get to drive a lot of Omegas), despite its 160k miles and 11yrs (and hard life

)
Obviously, everyone has different ideas about servicing, so I can only advise what I would recommend, and what I personally do to my own cars
