Ditto what Eric said--I use Mobil for the same reasons.
Also, syn's don't thicken with cold like dino's do. They flow cold the same as they do hot.
Something I haven't seen anyone talk about is the bypass pressure relief valve found on all engines. When dino oil is very cold, there is a piston shaped valve with a spring behind it in line with the oil filter, which opens if too much pressure is encountered there. It diverts the oil from the filter to the mains etc so there won't be starvation and so it won't over pressure the filter.
In old VW engine hopups (and racing engines) we used to put in a much heavier spring to keep this from happening.
Modern engines started using lower and lower viscosity indexes because of this. The first number in 5W30 indicates the flow rate at a certain temp--the lower the better. The second number indicates the film strength at a certain temp--the higher the better. It is the film strength that keeps your mains from grinding. The flow rate is of course for everything else that needs oil ASAP.
There used to be a few kits around that allowed you to pressurize your oil circuit before cranking--as this is where most of your wear is encountered because of starvation. I have often wondered why OEM's don't include this stock.
But, the bottom line for me to use syn's are:
The flow rate when cold.
Syn's don't drain down as dry when the engine is sitting.
And the film strength when hot--that is where dino falls behind syns.
