I've recently been thinking about the question of rationing.

Now I've suggested in the past that I expect to see 'rationland' effects, as government attempt to react to decreased availability of oil on the open market by slapping limits on usage. I've said that sensible though it sounds, the net effect is to steepen the decline rate for the 'have nots', in other words you and me. That increased decline rate limits the time to adapt to changed circumstances, making things more likely to break than bend.

I still expect them to do it.

However there is a tweak here. There are effectively two fuels, petrol and diesel. Although you can tweak the refining process to change the proportions produced, it's only within bounds. You will still be producing both, no matter what.

Now diesel is used in the long distance trucking, buses, trains, larger scale emergency generators, etc. - all the types of usage that will be key in a future, more resource constrained, world. Therefore a large percentage of production will be allocated to key users - making domestic diesel users very much on the wrong end of rationland effects. That's particularly important for Europe where diesel cars outsell petrol.

Petrol on the other hand gets used in domestic vehicles, particularly in the US. Although there are emergency and delivery van users, a much bigger proportion are 'non critical'.

Therefore as we coast down the resource slope, it might be that a petrol car is more sustainable than diesel - especially when rationing hits. Best bet I think is probably going to be a small, efficient, petrol vehicle (but 5 seats for ride sharing), together with an old diesel flatbed truck which you don't use most of the time, but which gives you options in 'rationland' and can also be employed to shift stuff around on the rare occasions its needed (a favourite excuse for having an SUV).