Short answer - I would'nt buy a car in Singapore...
It way too expensive if your are an expat who will only live here for a few years....
Though that said, there are deals that allow you to afford a new car by monthly payments but when you think about the instant money lost after purchase or when you break even on the repayments to get a new car I can't see the logic in it...
The Buses and MRT in Singapore are great and taxis are pretty cheap - Why get all the extra hassles of ERP, expensive parking fees, etc, etc???
