I personally believe it's whatever the car seems to like, run good on. If your's is new, I'd most definitely run what it calls for new, at least until you're warranty is up. After that, it's up to you.
But, I have a now 165k mile vehicle, my highest mileage one that I currently still own - had this truck since day one. When it was built in 1997, they called for 10w-30, that's what I ran for a solid 6.5yrs & 130k miles without issue.
Just in the last few years of moving back to Colorado - and colder winters, I have started running 5w-30 in the winter and 5w-40 or a mix of 5w-30 & 15w-40 in the summer.
Truck seems to prefer thicker oil in the summer, I did try to run 5w-30 in the heat of summer the first winter I tried it, but after pulling our boat for 1k miles with rpm's ranging from 2-4k, the idle psi dropped extremely low and truck starts to tick.
However, look at your owners manual and see what it recommends for different outside temperatures; mine specifically states not to use 30wt oils if the outside temp is above 90F - but I've never really had an issue.
I have not experienced any leaks, nor do I use any oil.