PT144 · S4 · Q8 Satellite navigation systems (satnavs)

This is just telling us who is more likely to use satnavs, and unsurprisingly it's drivers who are frequently going to new destinations and thus need directions. But that doesn't tell us anything about whether those drivers are saving fuel or being safer by having a satnav vs. a paper map vs. any other means of finding their way.

No Impact: wanting to find shortest route Like (A), this answer seems to just spell out a common sense fact, which means it won't really have any impact on the argument, since we already know common sense facts. Naturally, the more of a gas guzzler you drive, the more financial incentive you have to keep your trips as short as possible. But that motivation applies to all drivers. No one is generally interested in spending more fuel or time than they need to, so everyone is generally interested in finding the shortest route to a destination. Presumably, satnavs are giving you the shortest route they can find, and people using paper maps are seeking the shortest route they can find. Since everybody is motivated to find the shortest route, this doesn't provide any distinction between driving with a satnav and driving with a paper map, and thus it gives us no additional way to argue that driving with a satnav is more fuel efficient or safer.

Like (A), this is just telling us who is more/less likely to use satnavs. This answer makes it sound like people who usually don't need to drive somewhere new are more likely to plan their route carefully prior to departure (which sounds like they're neither relying on satnav to guide them nor checking a paper map while driving to figure out the next turn). These people seemingly aren't using satnav or paper map, so they have no bearing on whether using a satnav would tend to make a driver save fuel and be safer.

This is talking about people who use satnavs. Is it telling us that they're saving fuel or being safer? No, it's saying they usually don't bother using their satnavs. They already know their preferred route, so they don't bother turning on the computer to boss them around. If people who drive cars with satnavs aren't using the satnavs, then we aren't going to be able to argue that the satnav is saving them fuel or promoting safety.