The 5w30 oil I have been using is semi synthetic from Castrol, the manual says it recommends 10w40 or 5w30 is ok if temps fall below -10. The only reason I got 5w30 in the first place was because I didn't have the manual at the time and was in Halfords and they suggested this :/ now I am starting to think I need to do a complete oil change, last thing I want is to cause something to go wrong in an old engine if the weight is wrong

 

this looks a good buy

 

I would recommend 5W30 full synthetic or 10W40 full synth wil work too as long as you are not living close to the north pole. but I would definitely NOT go for the cheapest oil brands possible.
The difference between a good long lasting oil and a soon depleted, less performing oil is in the additives (the dopes)
A-brand oil companies put a LOT research and effort into the additives in their oils to beat the competition and that makes their products more expensive.
In almost any case A-brands are worth the bucks in my book.

 

Thanks vmaxxer, I shall keep it in then until I do its next oil and filter change in the spring, I thought comma would have been a good idea as I already get the anti-freeze and ATF+4 fluid from them but I see your point that companies such as Shell, Castrol would of course research more into additives to aid the engine parts etc
one question I have is what oil filter do you use? when I search for them online there seems to be many different varieties.
Only had my GV 7 months so not done a change on it yet

 

I have never heard of Comma, could be not too bad though, but personally I stick to Shell. lately I did some price research and Valvoline came out pretty good in price<>quality comparison
I use Mann filters, because I am used to that brand in my other car (Mercedes)

 

Thanks, I am going with the shell Helix Diesel HX7 I shall try the Mann filters out also.

 

What ever grade of you use, I would definitely use fully synthetic. As mentioned the turbo bearings get very hot.