putting unleaded in a diesel car

Short answer: it’s bad. If you’ve put unleaded in a diesel, do not start the car—don’t even turn the ignition on—because petrol strips the lubrication a diesel pump needs and can grenade the injectors with all the grace of a lawnmower in a nail factory. Push it to a safe spot and call roadside assist or a mobile mechanic to drain and flush the tank, lines, and replace the fuel filter. If you haven’t started it, you’ll likely escape with a clean-out; if you have, budget for a new pump/injectors and a bill that can stretch into the thousands in AUD. Keep the receipt—some insurers cover misfuelling, if you’ve ticked the right boxes. Next time, slower at the bowser; caffeine can wait, high-pressure pumps can’t.