This is a newbie Q, so please bear with me. The last 3 times I've had to switch to reserve, it has been at 141 -142 miles. The most recent fill-up on reserve was at 173 miles - much more than it should have been, considering that the reserve is less than 1/2 a gallon and I have been averaging 47 MPG ( so an additional 24 miles max). At fill-up I turned the petcock back to "vertical" (pointing downwards), and expected to put in at least 3 1/2 gallons, but it took only 3 gallons. When on reserve and filling up, what position should the petcock be in - pointing downwards, pointing forwards (on reserve) or pointing back (closed)? Thank you in advance!