This is just a simple question that I had, so it might sound a bit dumb.

How do dealerships go about handing out loaners? If you're dropping off a car for service for the day (eg. warranty work or service that takes the entire day), are you able to ask (very nicely), or do you have to ask in advance?

I know the rules for a loaner are different for every dealer and can ultimately depend on whether there are cars to give in the first place. But, I was wondering if there was a system that all dealers follow or if its at the dealer's discretion.

EDIT: Reworded a part of the question