Orkekum wrote:I heard rumors about s&r ships will refuel you
Well, I can confirm that they can refuel you. I just don't know what the triggers are. So far, it's only worked in a high security system where I'm allied with the local faction. The rescue ship appears near a planet with a RES when your main fuel tank is drained and you are in SC or when you enter SC. You will get 1-2 messages, and if you select his wake from the contacts panel you can fly over, exit SC, and he will give you a bit of fuel.

I've also tried other systems where I may or may not have been allied (I don't think I was), both high security and medium security, with and w/o planets with RES sites, and I never got another rescue ship to appear. So I'm thinking being allied may be the key, but it will take some more testing. I didn't see any threads at the main forums about this. It may also require the nearest station/outpost to be a certain distance away. When I got refueled, the nearest station was quite far away. All the other places had stations within 200 ls.
***edit***
I should add that I had previously seen S&R ships in a USS or two in the system where I was refueled - they were exploring wreckage.