UK Car Repair: vauxhall estate cracked piston enquiry, head gasket problem, vauxhall astra

Question
QUESTION: My vauxhall astra diesel estate started sending out white smoke a few weeks ago and then misfiring and becoming difficult to start
My garage found that all oil had gone and suspect craked piston It is P reg and has done 90000 on the clock
is this likely to be the reason Can I still drive it if I fill the oil up and is it wirth repairing?


ANSWER: White.smoke.is.usually,water.or,brake,fluid,did.they.do.a.compression.test.When.did.you.last.check.the.oil?

---------- FOLLOW-UP ----------

QUESTION: the garage said that there was no oil in it when I left it there It had been making a noise tyhe day before and that is why I took it inThe white smoke started 2 weeks ago It had major oil change last year and I have checked it since then but not every week! The head gasket was changed by them last year But they say that that is OK
What do you think?

Answer
A lack of oil would cause serious problems on the bearing surfaces such as the crankshaft and camshaft and you would hear it knocking very loud.  It is hard to imagine how a piston could be damaged unless the engine overheated!.  As I said, white smoke is water, I would suspect a head gasket problem is much more likely??