On the Astra. Put some new plugs in 1000 miles ago, just checked them, and this is the result:
Plug 1 - very white, with a few bright white deposits
Plug 2 - exactly the same.
Plug 3 - very very black. Some traces of wet oil on the spark plug thread.
Plug 4 - very white, with a few white deposits.
Car symptoms - puffing blue oil when revved after idle, or when cold. Doesn't puff oil when kept at high revs.
Spark plug 3 - would you say this blackness could be related to a crap stem seal(s) above this chamber?
Re the other plugs being very white - does this show that it's running lean? Or maybe too hot? (or both?).
Bearing in mind the car spends all it's life on LPG, I'm not even sure if they may be normal.
Compressions are all at 13.5 bar.
Do others agree it's time to take the head off for further investigation?
If I decide to do the piston rings at the same time - can I do this with the engine in the car? Is it literally a case of take sump off, unbolt piston and remove it from the top?
Thanks all, your replies are appreciated. I've never owned an Astra before and after this, possibly never will!
Shame, 'cos it's nice to drive!