When I first started reading this thread, I thought to myself how lucky I must be getting upgrades as a 5* on most of my rentals. For that matter, when I say "upgrade", I mean automatically done, with the car waiting in my pre-assigned space.
My last couple of rentals, though, have been less pleasant. In PHX, I found a Taurus in my space (for a full size rental). I asked about an upgrade -- or, really, anything other than a Taurus, and they gave me a Camry. The Camry did have NeverLost, but I don't think that they had intended that to be my upgrade.
At EWR this week, I found a Toyota Matrix in my spot (on a mid-size res). It seemed awfully small, more like a compact. I asked if there was something else that they might have. I was offered a bunch of SUV's, but they eventually came up with the Hyundai XG350. Ironically, it was the same exact car that I had returned to LGA a few weeks ago (I guess maybe that is when you know you have been traveling too much - you get the same rental car that you returned elsewhere).
So, I have still been getting upgrades, but it now seems like I need to ask at the counter to make it happen. What is most strange about this is that both of these locations had PLENTY of cars available when I picked up. It seems like the opposite way hotels operate -- when there are fewer rooms, upgrades tighten up, but when the hotel is empty, they will gladly give you the Presidential Suite. For Hertz, when they are almost out of cars, it is easy to get a good upgrade, but when they have a lot full, they want to stick you with something less desirable. Doesn't quite make sense.
Stevekoe