If you just bought it, I'd go for an inital change of supertech 5W-30, with a pint (half quart) of MMO in the oil....BTW, have you checked the oil cap and/or manual?
According to Amsoil garage, this vehicle specs 5W-40.....but optionally, you could reference the temperature guide
-13 To 84 F......10W-30
16 To 68 F......20W-20
32 To 102 F......30
Above -13 F......10W-40, 10W-50
Above 16 F......20W-40, 20W-50
Above 84 F......40
Below -4 F......5W-20
Below 32 F......5W-30
The guide at
http://www.kia.ca/content/Owners/OwnersManual/2002_Sportage_Owners_Manual_EN.pdf (note: Canadian Kia site..) shows 10W-30, 10W-40, 10W-50, and 5W-30 being all acceptable fluids.
So it likely could be simply differentiated since they can't take into consideration how people will be using the vehicle. If you are towing, I'd go with a higher viscosity oil.
On a side note, I'm surprised the vehicle specs Dexron
Not the "Diamond SPII" stuff that mine specd