Fuel stations Karavanke → Koper is a 150 km transit route along the A2/A1 and takes about ~1 h 30 min. The cheapest fill-up comes from leaving the motorway — for example at Jesenice — where regulated prices apply.
Regulated prices for petrol 95 and diesel in Slovenia change every 14 days, on every second Tuesday.
An electronic vignette is mandatory to drive on Slovenian motorways.
Take the exit at Jesenice and refuel off the motorway — regulated prices apply there and are lower than at motorway service areas.
Fuel in Slovenia is usually cheaper than in Austria — fill up right after crossing.
Summer traffic towards the coast is heaviest on Saturday mornings.