Zipcar is still your best bet.
The majority of auto premiums are based on personal liability more than the value of the car. If you're driving a Hummer and get in a collision, it'll cost them the Hummer and a bandaid. If you're in a 1993 Taurus with a rusted up frame and torn up windshield-webbing, it'll costs them six digits in medical.
Cheaper car does not necessarily equal cheaper premium.