Driving from Germany via Salzburg or Villach to Croatia, you cross Slovenia on the A2 or A1 motorway. Slovenian regulated off-motorway prices are usually the lowest on the whole route from Bavaria to the Adriatic. Refuel right after the Karawanks tunnel or after Šentilj.
Yes. Regulated Slovenian off-motorway prices are usually below German and Austrian prices, making Slovenia the best refuelling stop on the way to the Adriatic.
Yes. A separate Slovenian e-vignette is required for motorways and expressways.
On the A2 around Novo mesto, and on the A4 in Ptuj or Podlehnik before Gruškovje.