I wouldn't run 20w50 in a "newer" vehicle. Especially when you know it takes 5w30.
Save yourself a lot of trouble and do a simple google (bing) search on oil viscosity - there are pages and pages of info out there.

In the "old" days" the general rule of thumb was the higher the number the better. But that thick oil actually consumes horsepower!

Some new cars today actually use oil that is listed as 0w30 and 0w20! Again, I'd say do a simple search all the info is at your fingertips and also search API index, more good info.