As MDG states, Millers are well regarded as are Motul and my local Subaru dealer uses Castrol Magnatec. TBH though, most decent fully synthetic oils should be fine for turbos and semi-synthetic oils for non-turbos will be OK.
As for the grade, it can depend on local temperatures but in general 5W30 is as thin as you want to go and 15W50 is probably as thick - as MDG says, 10W40 is a good choice.
my last full service by the main steeler over here used total quartz 5w40 , the last oil and filter change before that i did myself as it was an intrim i used comma and genuine filter which was very good imo........
In some cases... the older the engine, the more worn the piston rings / cylinders, the more oil your likely to burn. As a thicker oil is harder to force past the rings, in theory, the less you'll burn... some say a 5W40 oil is too thin anyway - my local specialist (S4U) uses 10W50 oil.
Sometimes, mineral oils are recommended for higher mileage engines too... something about helping to soften the piston rings and helping them fit more tightly in the cylinder.