Some of those internet photos are a bit old
@DaveB
I have friends who used to run the Tjukaylrla Roadhouse. There are a number of places between there and Yulara where you can get fuel - Warburton, Docker River etc but only “Opal” Petrol and not unleaded. Same thing really but it has an additive so that the local aboriginals can’t sniff it and cause themselves damage.
Other than the Canning Stock Route the longest distance I can recall without ANY fuel was on the Anne Beadell H’way between Coober Pedy and Ilkurlka Roadhouse which is about 780km, or nearly 950km if you do some of the side trips. I did that in a petrol 4.7L V8 landcruiser carrying 110L on the roof.
The reality is that there are only half a dozen remote outback trips now where you really need to carry fuel, but yes having a diesel helps with the worry factor of running out, and if you need emergency fuel local properties will have diesel and not unleaded.