Isn't that slightly ambiguous
......an oils life depends greatly on it's use.
Oils offer a wide range of interesting topics of discussion but like many things in life, it's somewhat a case of swings and roundabouts. Everyday driver?.....high performance engine?..reduced cold start wear?....good high temperature protection?....service intervals? to name a few.
I personally wouldn't use a 0w-40. Although a 0w-40 maybe synthetic, it offers very little advantage over a 10w-40 synthetic in terms of viscosity reduction at startup and the latter has the benefit of having less viscosity improving additives which have their drawbacks. A 10w-30 would offer a slight reduction in viscosity at operating temperature but at the expense of engine wear protection. I am splitting hairs but oils are complex and unless you read up or spend time as an oil analyst it's not always an easy choice.
All that aside, the key with all multigrades is to make sure oil is changed appropriately......you don't want it to degrade to the point of a 10w-40 behaving like a 10w-20 or even an SAE 10 grade.
