Civic Vx Shift Indicator Light (SIL) problem

[GasSavers_ElCheapo]

First the problem: My sil stopped working when accelerating the car. I.e. driving. lol. It still lights up at start up so I think the light itself is ok. No cel(s) or anything. Any suggestions? Fuse? Relay?

Second: What is the main purpose of the sil?
1) Is it to show the OPTIMUM time to shift as far as milegage?
2) Is it to say: "ok shift now, you've gone far enough"?

As to the above two questions: please state:
a) Your opinion
b) Your actual experience. lol

Tia!