It will perform like all other 30 weights in hard running.
Just cuz its a 0w in front doesnt make it any thinner when running hard than the other 30 weights (10w-,5w-).
In general a oil with a bit larger vis spread like a 0w-30, needs more VII's and you might see less stabilty, but with the quality of base oils used in this oil it becomes a non issue.
So if your engine specs out at 5w-30, 10w-30, it meets the vis req'ment for the warm running portion and exceeds the cold start req'ment.
Having said all that, here's my soapbox:
Many many oil recommendations nowadays do not increase the recommended viscosity for sumer drving, this is purely a function of CAFE and not due to some magical decraese in bearing clearances during the early to mid 90's when this bad habit took root.
Those of us that drive engines that have been around for a while can simply look up the recommendation for them in the late 80's, which ofetn list a number of temp ranges and recommend oil for them rather than a single (thin) grade all year.
Also some engines will have a thicker recommendation in other countries than here, in USA(!) even if same engines.
For example the BMW straight sixes recommended 10w/15-40 in summer, or 15w/20w-50's in hot summer, conditions in the 80's.
Now very much the same engines, recommend 5w-30 year 'round even in the US summers..
In summer, I never run less than a 40 weight oil in my Q45 (5w-40), and when in the southwest in summer a 15w/20w-50.
Actually, even in a (milder, kentucky) winter, I will leave in the 5w-40.
Fred...
[ December 15, 2002, 10:59 PM: Message edited by: palmerwmd ]