Has anyone had success getting a guaranteed 135i or 123d rented to test drive while on a trip to Germany? I lived in Munich for six years, speak German and return every year usually renting Audi A4ds from Auto Europe since I have figured out how to get one of those with about 98% assurance by scheduling the right class of car through Auto Europe (contracting with Europcar in Germany) and starting the rental on a Saturday in Frankfurt or Munich when all the business renters have returned their cars. But, I have yet to find an agency that will provide the BMWs that interest me. Europecar usually offers 320s. Any success stories?
You might try Sixt. It's been a few years since I've been, but on previous trips I've been able to get BMWs in Munich or Frankfurt. It would more likely be a 118 or 120d hatch, not 123 or 135.
European rental cars definitely tend to be the low powered, high mpg versions in my experience also. It always sems to be a crap shoot with car rentals. You get whatever they have and there is no way to know what will be available until you are standing at the counter. I've never used the Hertz "Green collection" but they did screw up my rental several times.
