Blue smoke from the exhaust.

Well, just noticed the other day when I was stuck in traffic. The car heated up a bit more than usual (fan came on). I then drove away from a junction leaving a cloud of light blue smoke. I know this from common sense to be oil, but is it the valve stem seals or the piston rings? I have been given the impression that piston rings give smoke on acceleration, while the valve stem seals give smoke on the overrun. It only happens when the engine gets to normal operating temp or above and I blip the throttle. If I move off very gently it gives off hardly any smoke.

most likely to be the valve stem oil seals, the reason it only does it when warm is that oil is too viscous to pass them when cold. you can check the condition of the rings by performing a compression test.

Valve stem seal are the most common problems.

Cheers guys, i'm replacing the timing belt and rocker cover gasket so might grab some seals and do them while I'm at it. Mr Haynes says you can do it without taking the head off so I might have a bash.