Fuel stations Trieste → Ljubljana is a 95 km transit route along the H4/A1 and takes about ~1 h 10 min. The cheapest fill-up comes from leaving the motorway — for example at Nova Gorica — 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 Nova Gorica and refuel off the motorway — regulated prices apply there and are lower than at motorway service areas.
Fuel in Slovenia is substantially cheaper than in Italy — fill up right after the border.
Strong bora wind can hit the Razdrto–Vipava section — drive carefully.