Far out I'd sell it and get a Diesel if you want to do big miles. cost wise it'll cost you a fortune for gas if you can get it at all and maybe $2.50 for ULP
I have 165 ltrs of diesel and think taking it easy on the roads you mention I should get a 1200 range at a cost of around $300 a fill

Do the Math
Dont think you can carry ULP inside the 4x4, fumes