We just spent two weeks in Croatia. Absolutely marvelous place! Recommend!!!
Rented a Peugeot 5008 with a 6-speed, and drove it from one end of the country to the other Zagreb to Dubrovnik. About 400 miles. The most AMAZING drive of my life. The roads are so narrow and fast that I was constantly fighting the lane assist to not hit oncoming trucks. And the road maintenance Unimogs don't put out warning signs - you just come around a mountain bend and hit the brakes because there they are!
Anyway the awesome Peugeot (with folding tray tables and hidden storage under the floors) returned over 30 mph, despite speeds over 100 mpg and elevation changes up to 10,000 feet. On the whole trip I filled up once, and another 4 gallons before I returned the car to Sixt.
At $9/gallon, I didn't mind one bit.