CAN SOME ONE EXPLAIN WHY MPG DISPLAY DOES NOT ALWAYS SHOW YOUR MPG, I TRAVEL 22 MILE ON MY COMMUTE TO WORK, THE DISPLAY SHOWS BETWEEN 65 AND 95 MPG DEPENDING ON THE TEMPERATURE OUTSIDE (GX3) WITH AVERAGE ELECTRIC USE OF 75% BUT SOME DAYS THE MPG JUST SHOWS -- - NOT GIVING ANY FIGURE. I WOULD...