Not sure if its been asked, sure it has, but couldnt find it doing a search.
So out for a spin w/a mate on the auld bog roads of the Wiclow mountains(most of the road was done in 3rd gear @ low revs, mate is a learner & roads are tight & lots of sheep), surprisingly the red light came on

Didnt have a clue where we were or where the closest petrol station was. When we finally got to one I filled up & too my surprise she only took 13ltrs(15miles after the light came on)! I was under the impression that it would be 14/15 & the rest to reserve
So the question is, how much should it be before the red & how long do you get on reserve
Cheers in advance
