It is not advisable to rent a car in Istanbul as traffic is horrendous, the parking places are scarce, and the gasoline is expensive. Use the excellent public transport and taxis. A car is a liability for tourists in İstanbul! I've only rented a car there once and that was for a visit to Edirne.

It's best to avoid driving in big cities such as Istanbul and Ankara as traffic can be very chaotic. In central and eastern Anatolia, the roads are often in bad condition due to heavy traffic and harsh weather conditions. If you're driving at night, or in rural areas, watch out for livestock and unlit farm vehicles.

Good to know when renting in Istanbul Renters with licenses using non-Roman alphabets like Arabic or Cyrillic also need an international driving permit. The minimum age for rental in Turkey is 21 with a license held for 2 years.