The Mongol Rally isn't about comfort and it doesn't have a great deal to do with style. The whole point is that it's difficult, so big 4x4's are completely unacceptable! To tackle the worst roads in the world you must have a 'car' with an engine size of under 1.2 litres (ish). At the end of the rally the cars are auctioned off, with all the money going to the rallies official charity The Lotus Children’s Centre.
There is a 10 year old rule, which states that cars should not be older than 10 years old. This was set by the Mongolian authorities, mainly to prevent a trail of deserted 25 year old rusting Fiestas stretching throughout the Kazakh desert & over the Pamir Highway.