so i put about 3/4 tank of gas in my car lastnight. 93oct as usual. drove it all around yesterday and no problems. get in it this morning, drive over to my friends house. no problem. get back in, and my gas guage reads 10mi to empty. wtf. now it keeps going down like im running out of gas but i know it has gas. and as it reads lower mi to empty, my guage climbs back up to around 1.4 tank. so whats wrong with it?