Just for info, after you enter Romania via Arad you have another 350km of highway, then a 170km break (mountains, bad traffic) and another 100km before Buchares

Just for info, after you enter Romania via Arad you have another 350km of highway, then a 170km break (mountains, bad traffic) and another 100km before Bucharest. 600km that you can drive in 4.5 hours on highway takes over 8 hours. If you enter via Oradea, it takes even longer. 15 km in Bucharest at rush hour takes 2 hours. If you want to come, you are welcome, there are some nice places.