How far can you go before you run out of gas? the fullsize is suposto have a 30 gallon tank.... but i cant make it to 400. so i suspect my odometer is bad. it locked up on me not long ago as well. or the tank pick up/sending unit is toasted. it does tend to be rather erratic...and when it touches the color- done. so to anyone with the fullsize blazer, tahoe, yukon, how far does your tank get you? thanks!