Motor vehicles after a century and a half of abuse

I'm writing a fantasy novel that occurs 150 years after the obliteration of a civilisation with mid 20th century level technology. People's survival in the years that follow rely heavily on salvage of crucial supplies from the bones of the old cities, military supply depot, etc. Until now I assumed that they would be needing to use animal drawn carts and wagons in trade caravans and salvage teams to carry supplies across the extremely dangerous wasteland, but it occured to me that they might have motorized transport left. I'm thinking something like an old pickup or truck that's been carefully maintained over the years and modified for the situation, maybe dragging a few conventional wagons behind it. Fuel is an issue, but the salvage teams are heading out to look for a type of special fuel used in the pre-cataclysm days, so there's no reason they can't pick up some diesel while they're at it.

Some properties the vehicles would have:

• Would not need to be able to move much faster than a human can walk or run. Properties of the wasteland inhibit moving fast if you wish to retain your health, and the roads aren't in good shape anyhow.
• They'd need to be able to provide shelter for a small group of travellers, their supplies, and whatever they haul back with them.
• Need to be robust against attacks by primitive raiders with stone age weaponry.

While the surviving people retain metalworking and salvage for materials, they're going to be sharply limited in terms of quantity and quality of salvage, so replacement parts are going to be difficult to come by.

Would a vehicle have been able to survive and still function after 150 years? With mediocre capacity for restoration at best, what kind of shape would they be in? One of my characters is a mechanic, so how many times would she need to be cracking open the hood in a month of travelling? What would the fuel requirements look like, especially with an old frankenstein of an engine? Are they any neat things that I could use these old ramshackle vehicles with that I might not have considered?

Thanks!

Thanks guys, that's great information.

How would one go about creating bio-diesal? What kind of supplies and equipment would be necessary?

The nature of the setting makes keeping livestock questionable. Habitable space is at a premium, and while the livestock can likely survive to some extent outside it, it would be very expensive and very dangerous for the handlers themselves, likely necessitating that valuable living space or farmland would have to be given up for the animals. It's not impossible to deal with, but I wanted to explore the possibility of mechanized transport. At least on the surface, it seems like it would solve several logistical issues with feeding, sheltering, and managing the number of animals needed to run a number of simultaneous caravans.