Here is a quick tip to save some money on the expensive Slovenian highway toll if you’re driving from Belgium/Netherlands/Germany to Istria in Croatia.
From Villach in Austria, drive to Trieste in Italy which is right on the border with Slovenia. Keep driving on the highway, through the (new) tunnels. Pay attention to the signs that warn about the last motorway junction before the border/toll. Take this junction (Muggia). Now you have to continue the old road to the border. (follow the signs Plavje, Skofije, Bertocchi and then Pula). Make sure you don’t accidently get on the highway again, which runs parrallel.