Running old 3-way fridge-gas usage!!!!

Hey guys, picked up an old 3-way electrolux fridge, had it serviced and it runs like a beauty!!!

Problem is how long will it run on a 4kg gas bottle, was hoping someone out there may have a similar old fridge, or an easy way to figure it out. We're spending 5 days on Fraser Island and would hate to have the gas run out.

Here are some details
Mod. No. RC 160 A EGP
Gas Propane 2,75 KPa

Thanks in advance
Steve & Sandy
All my friends have Nissans
I'm the rose amongst the thorns