Depends on the dealer, mostly.
I had my '18 GT2 in for head unit, headlight adjustment, and fixing hood latch - was told it would be 6-7 hours. When I made the appt I was offered a loaner.
Reminder call for the appt, no loaners. 1 service advisor said Kia doesn't give them enough loaners. Another service advisor admitted that the dealership is up to their eyeballs in 2.0 recalls and their entire fleet is out.
Kia corp said they should at least have an agreement with Enterprise for local rental, which dealer didn't do or offer. Kia corp did send me a box of chocolates tho.
The car is great, but I got better service with my 2011 Optima.
-Greg C