Hi there,
the 10w30 would be a heavier oil. On a multi viscosity oil, there are those two numbers on the can. The first number is what the viscosity would be at a cold temp, the second is the viscosity at a higher temp ( I think the temps are 40 and 100 c they measure at) So basically, your oils would be the same at around 212 degrees, but at 100 degrees the 5w30 would be thinner than the 10w30.
Hope this helps
sam
Technician/Shop Manager
ASE Master, L1 cert, 25 years experience domestic & import