Sometimes when I stop at traffic lights or anywhere heaps of dark grey smoke comes from my exhaust, then when I drive off it will blow a little bit of light grey smoke for a few seconds and then stop. It doesn't have an oil leak but it has used 2.5 litres of oil in the last 2500 kms. I filled it up today, and that's when I have noticed the smoke again. Anyone got any ideas? Blown head gasket? It's a gen 2 3SGTE.