As some might know I am in the middle of planning my 5 month trip to Europe this Spring and summer. In that process I am renting cars in France (Paris), Italy, Montenegro, Bulgaria and Slovenia. Some cars like those in Italy and Bulgaria for as much as a month each.
What I've found is very interesting. While Croatia is pretty expensive for car rental, Montenegro is very cheap to rent a car. And it can be driven to Croatia. My rented AVIS Economy car for 7 DAYS cost $100.79. The same is true for Slovenia. Renting a car in Ljubljana is much cheaper than any neighboring country. 11 DAYS for € 138 for an Opel Astra. And if you rent in Slovenia you can drive that car to all of the EU and the bordering countries.
Italy was the most expensive. Bulgaria was easy and cheap $444 for 29 days.
So if you are headed to this part of the world and want a rental car, search carefully and choose the country of your rental strategically. I have been using Kayak and found that I get the overall cheapest prices there. Of course Kayak just sends you to the cheapest aggregator. On one occasion I found the cheapest price directly with the rental car company.
**All prices are all inclusive of taxes and fees and unlimited mileage.
I hope this can be of use for someones planning.