$carQUERY=mysql_query("SELECT tanks, mi_start, mpg_start FROM cars WHERE cid=$cid");
$car=mysql_fetch_array($carQUERY);

// Grab tanks data
$tanks=0;
$tankQUERY=mysql_query("SELECT mi, mpg FROM tanks WHERE cid=$cid AND deleted=0");
while($tank=mysql_fetch_array($tankQUERY)) {
	$tanks_bit=$tanks_bit + ($tank['mi']/$tank['mpg']);
	$mi_tanks=$mi_tanks + $tank['mi'];
	$tanks++;
}

// Define car data
$mi=$car['mi_start']+$mi_tanks;
if($car['mpg_start']>0) {
	$mpg=$mi / ($tanks_bit + ($car['mi_start']/$car['mpg_start']));
} elseif ($mi_tanks>0) {
	$mpg=$mi_tanks / $tanks_bit;
} else {
	$mpg=0;
}