A lot of times various weights of oil are meant to satisfy the major automakers specs on bearing/ring tolerances in new car engines. I have not tried the newer Mobil 1 synthetic weight oil but I have always used the 10w-30 myself. The Mobil 1 SuperSyn oils are a response to the recently released reformulated Amsoil as of about 4 years ago. Those two seem to go back/forth. There really isn't anybody to compete with except themselves for the top quality oil. I don't just use it because somebody else does or because it's cool to use it and spend the money, I know the numbers behind the oil and when you have knowledge backing your opinions and experience, it's hard to debate it. By accident I have overheated three different motors and the latest was my wife's 1999 Blazer and it leaked out about 75% of it's coolant because of a bad intake gasket. I decided to try and limp it home anyway. The temperature on the gauge climbed to 260 and I drove it like that for 25 minutes until the motor started to detonate from excessive combustion chamber heat and then the gauge just fell to zero and would not read the temperature any longer. The Blazer was losing power bad.....it started to sound as if the rod bearings were all banging at once. I would floor it, and the truck would not hardly move anymore. The temperatures were so high that the knock sensor was retarding the timing back due to the cylinder head heat an the truck would not go...so I coasted onto a side street and when I shut the truck off-the remaining coolant in the motor that could not circulate just blew out of the back of the intake, onto the exhaust cross-over pipe and there was smoke everywhere. I thought the motor was smoked. Later that day, after it cooled enough to move the truck, I started it just to put it into position to start pulling the motor, and to my surprise, it started and ran just as smooth as if nothing ever happened. There was no smoke, no knocking, no ring flutter, no wrist-pin rattle-nothing, just a smooth running engine. I went ahead and replaced the intake gakets, changed oil, tranny fluid and added coolant. No problems. This motor had 159K on it at the time and I have used Mobil 1 5W-30 in it since we bought it with 98K. This is the third and most hair raising overheating story but each and every time I've ran Mobil 1 and I think it has now saved a motor three times for me. Knowing what I do about Rate of Evaporation, I don't worry when I lose all of my coolant-I know I have at least 10-15 minutes to drive it somewhere...unless it's computer-controlled...lol. I would not trust ANY conventional oil to give me that kind of protection and very few other synthetics. Again, my observations and opinions are derived from experience supported by facts. Oh, and afterwards I did do a compression check on the motor in the Blazer, all cylinders were between 111 and 114. Crazy.
To answer your question more directly, I would use a 5W-30 in your car because it'll flow very easy and resist the high amounts of heat that turbo will generate. Keep within the oil weight for the motor-going thicker will increase your oil pressure but that does not equate to better flow. Pushing thicker oil can and eventually will lead to easily avoidable problems. High oil pressures are like heart attacks-high is bad-keep it manageable to avoid a breakdown, or attack. Since synthetics flow so easily, it's normal to see 15 psi @ idle at operating temperature. 40-45 is normal on the highway. Anything over that and the pump is overworking itself, or, the tolerances for the pump are super tight. Oil pumps imo have a point of diminishing returns and I'd put the point at 45 psi max. This refers to a highly modified street car-you get into doorslammers and such and the world is quite different for oil flow/control.
Blew the oil seal on my turbo. 
