Thank you for your input (quite obvious that I would get what i pay for) but i think you misunderstand and its my fault as i did not specify... apologies. I am willing to pay for an upgrade. Are you saying that i would not be offered a paid upgrade at LAX unless someone is a diamond(whatever that is)? That just does not sound right. All car rental companies that i have used do offer paid upgrades. And some on here have even been getting some really awesome free upgrades(subject to availability obviously).

The reason I like to not book what I really want up front is because it would take away from my ability to negotiate a better deal face to face.

Hence my related question... If I have express service would they let me switch out the car if I do not like it or am I stuck with what Sixt express service has on the lot for me?