Bob asks if he should tick off a shotshell from his ammo counter. The GM says, "Nah, it's not really a survival scene so only a cock would have you do that. Besides, if I need you guys to run out of ammo, I can make it happen." Sometimes we should learn to keep our thoughts to ourselves!
While the haul wasn't as big as they would have liked it to be, the parts certainly are more than they had hoped for. Bob insists that Smythe keep the parts, ostensibly because she needs them more than he does. The real reason isn't that Smythe is a looker--she's not, and besides as one of the cowboys who keep everyone alive Bob probably has a couple of hopefuls back home. What's going on is that doing so will prove his goodwill. Or so he hopes.
It also makes up for the fact that they have to move at the speed of their slowest member--in this case the GM states the roads are passable, so it is the pack horse at 12km/h. (On the other hand, if going offroad, it's the trucks: 8km/h assuming flat and open terrain.) For going well below their capable speed, the GM decides the vehicles use only half their usual fuel consumption, same as idling. It's 7 and a half miles an hour, that's practically idling anyway!
The two trucks and two pack animals travel for 4 hours, making it 50 klicks before something noteworthy happens. Bob's hybrid SUV burns 1.9 litres of Gasoline (58.1L left in the tank), while Smythe's technical burns up 4 litres of sweet sweet diesel (leaving 66 litres in the tank).