If you have a vehicle that runs on gasoline, you don't have to store gasoline for a long time to have a stockpile.
The cost of a few empty canisters is by far smaller than the cost of solar batteries, and putting gas into a vehicle in case of an emergency within a span of seconds rather than hours is a huge asset.
Not to mention: not everyone has space for solar. City dwellers are particularly constrained (as in: people who live in apartment complexes).
Propane, sure, but now you're talking about something fairly exotic, at least in terms of vehicles you can buy "off the shelf."
In any case, you can't produce propane yourself. You can "produce" electrons with a solar panel.
Edit: My bias is toward North America, but I know of only one model of "normal person car" (city buses don't count) produced in the last 50 years that you could just walk into a dealership and purchase new: The Honda Civic NX. And that was sold for only a few years and only available in California.
But for conversations sake, if we're talking about diesel trucks, and specifically an old mechanical diesel like a 7.3 ford or a 12 valve cummins, and we're talking about stored diesel, ideally a class D died diesel with a high sulfer content, then you'll get considerably more lifetime out of it than the recommended 18-24 months.
Additionally, you can burn about anything, old motor oil, fry oil, diesel with algee in it if you treat it and change your filters. A good, mechanical, not very picky diesel will burn fuel that is 20+ years old. Not forever, and you'll go through some filters and maybe injectors. By the time you get to fuel sources that can't be burned in a machine like that, or you've burned it up past your parts and ability to repair. you'll probably have a lot of other problems.
If we're talking generators, you can get off the shelf propane generators and propane stores well.