In my experience, holidays and super late Monday nights are best for luxury vehicles.
I frequently rent from the same non-aisle location. You can’t even book a luxury class vehicle here. But, on holidays (Christmas, specifically) I’ve gotten a 7 series on a mid-size reservation. May have been just Christmas generosity.
Monday nights are good because most business and government travelers who are forced into midsize cars have arrived and departed with their reserved vehicles.
On late night Monday pickups, I’ve gotten Platinum Navigators, Q7, and XC90s. I had a 300C a few weeks ago on a midsize reservation. Crap car, but notable upgrade.
I learned the hard way, though. Any entry level luxury car is substandard compared to highly optioned domestic cars. A Fusion Titanium is better in almost every way than a 330i.