Driving to a friends home, had a 1/4 tank of gas. Was there an hour/2 got back in to go home & the the gas light came on saying 0 miles....... Drove a little ways & it ended up increasing to 30 miles...... I get the MPG's on my truck are terrible- but to go form nothing to something- is this normal??? Im new to the LR3 (a week) so please pardon my innosence......