What about a Corsa?
Same engine family as the Astra... And we all know how that's working out.
Yep 100% agree
but the corsa will probably have suffered even worse bad maintenance than an astra.
@ 120k semi synthetic or even mineral 10w40 would have been my choice.
little vauxhall engines don't like synthetic oil from my experience .
as for the garage flushing it , that is what you have done by putting in 5w30
yes you cleaned the sump ,BUT all the rest of the engine gunge from head,oilways and sides of the castings of the block etc is now dissolved, probably partly blocking the filter and pick up.
as with the last engine, I advise you drain it,new filter,new 10w40 semi or even thicker 15w40 mineral oil.
any car you buy needs oil suitable for the wear on the engine , I tend to buy lower mile cars and do cambelt and service etc .
important that a car has a credible documented service history unless yu know the seller. and it looks like the astras you have purchased have questionable history and high miles .
try the oil change and filter and make sure it is cooling correctly would be my advice . AGAIN