10w-30 is what is recommended for these engines, no need for the 5w.
on the subject of synthetic oils, they do not cause leaks, they will not 'clean' sludge from the engine. Old mechanics tale.
You challenged me on this line of thinking earlier this year, so I swapped 0W-40 Mobil 1 Synthetic into the 166k mile convertible. It went 2k miles and 4 months and was beat on a little. It did not develop any noticeable leak. So, I'm on your side until I see evidence otherwise.
I run synthetic in everything else I own... The higher-powered ones do leak, though. They never ran anything but synthetic, though. So that's not the issue.
On the "W" subject, that number primarily tells you how much the oil thickens at colder temps and thins at higher temps. All oils thicken at low temps. At operating temp, no matter what the "W" or even if it's just straight 30, they all act like a 30 weight. 10W will be thicker at cold start than 5W, and 0W. Just for clarity, though, All of the above will do just fine, but the lower the W the better the oil will be on cold start... the more quickly they'll be protecting your motor.
All that said, W numbers are not directly comparable from one weight to the next. The 0W-40 I run is still a thicker oil than a 5W-30 all the way down until around -35*C, based on Mobil 1 data.
All that said, OP, if you want to run 5W, or 0W, no worries.