I was driving a diesel, so after putting up with the stink of distillate after filling up from a high-flow bowser, I began to consider the relative merits of various fuels.
Starting with Diesel, it’s a lot cheaper than it used to be, and I understand is ultimately much more efficient than petrol. Modern diesel vehicles are pretty much on a par with petrol driven machinery when it comes to noise and smoothness. They also have heaps of torque, and are pleasant to drive, especially on long journeys. Fuel is usually easily sourced, even if you need to have a good cleanup after refuelling (especially in the bush) and are best dressed in overalls during the exercise.
Our fleet manager doesn’t like diesels but only for the somewhat bizarre reason that she’s sick of dozy drivers filling them with unleaded and driving away….very expensive.
I’d consider diesel on current prices, but they won’t last long. Once distillate begins to cost 15% above unleaded the benefits of improved efficiency disappear.
Most of us are familiar with cars running on unleaded, so I won’t go into any detail, except to say that modern small cars can be very efficient, and unleaded (particularly the ethanol blends) can be very cheap if you shop around.