5W-20 seems to be a popular recommendation for KIAs in the US, possibly for fuel economy reasons. Standard recommendation seems to be 10W-30 in Australia, and 5W-20 is a bit hard to come by. A quick check reveals that Caltex (for example) do not normally supply 20-Grade oils.
I use Caltex Havoline Premium Plus 10W-30 which has a viscosity index of 10.2 cSt @ 100°C, which is at the lower end of the 30-Grade range. If you do use 0W-20 or 5W-20, check that it does not have a very low viscosity index, since "20-Grade" covers the range of viscosities from 5.6 to 9.3 cSt. You will note that the 10W-30 oil that I use isn't much "thicker" than 20-Grade.
Last edited by Wry 'Cuda; 01-05-2013 at 08:32 PM.