In all fairness i fail to see why it's kieran's fault if he didn't realise.
If he knew then yes he's literally satan,
however the hole must have started as a crack, the crack might have wept a little whilst he owned the car and he might not have seen the crack. Then that chunk may have fallen out whilst you were driving, taking the rest of the oil with it.
Just playing devil's advocate before we all go on a witch hunt.
The best thing would be for keiran to show his face and tell us just how big that 3.1 litre puddle was.