I have always found that Mobil One 0W-40 is too thin for most cars, and when I worked in the trade use to recommend the Synta Gold or Castrol instead. A bloke I used to work with tried Mobil One in this RS Turbo (sorry for swearing) and it sounded like a bag of nails.
I do remember that Mobil also make an oil called Mobil Motorsport which was 15W-50 and fully synthetic. Had a look on the web and found that this is the only oil GGR (scooby tuner) recommend for all turbo imprezas
I ended up buying the synta gold after a long discussion with a very helpful chap at my local vw dealership. the bloke i spoke to was into modding golfs himself and covered in tatoos ( i was shocked as the parts dept is right next to sales in the showroom & and they all had suits on). 
And he recommened that i use either castrol synta silver or gold. it cost me ?25 for 5ktrs of synta gold and the castrol was ?22.50 halfrauds wanted ?39 for the castrol.
oh and oil filters are cheeper in the dealership thean in halfrauds too.
so the moral of the storey is main dealers can be cheaper for some stuff 
hi i have 2 full bottles of 5w -30 part synthetic. would i be ok using this as im needing a oil change and havnt got much money at the mo after xmas lol.the car has just done 65.000 miles? wat do ya think?
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