According to Mobil's website, the 5w30 and 10w30 have identical vis ratings at 100 deg C (10 cSt). The Mobil 0w30 is actually a tad thicker at 10.3. Go to Mobil's web site
But if you look at the virgin analysis, it is thicker than a 5W, not much, but middle of the road 30 weight. I like the 0W-30, it was a tad thicker but a really nice looking oil with killer additives. May have to give that stuff a shot sometime.