Evidently this situation varies at least by service center, and most likely varies according to the individual situation as well. So far (knock on wood), I have been provided a loaner by my local Service Center (Dedham, MA) each time I had service that was expected to take more than a couple of hours. (A couple of times, i have simply waited for the car.) Last year, during the Model 3 delivery blitz when the SC was super busy, I got an older Model S loaner and had it for 2 full weeks.) The most recent time, just 2 or 3 weeks ago, I was given a "loaner" that was actually an Enterprise rental car, a recent low mileage black Model S75D. The Enterprise agent was on site at the SC, and I was in the car and off on my way in just a few minutes. I did get a credit card charge for a tunnel toll (I forgot to grab my transducer from my own car), but otherwise had no expenses. I think I had the car for about 2 days (my car was having an A/C repair). That was the first time I had ever had an Enterprise loaner. I was not surprised to get one, because I have been reading about people getting them for two or three years, I think. My car is still in warranty, and that probably makes a difference. We will see what happens when the warranty ends in 3 weeks or so!