I have 2015 WRX base model and I just found out the the instant avg mpg gauge(the middle one) fluctuates down by less than 1 and keeps increasing....it was reading around avg 60mpg and keeps climbing up with slight fluctuation. I initialized the gauge to factory condition and still doing it. I'm getting 40mpg avg on city lol and if I drive longer, it will keep increasing. there is no check engine light or anything. I made an appointment to check that out with Subaru dealer. Is this normal?