If it is as serious as porosity, you need a whole new engine, they
can't fix that in the shop.

They won't give you a new car, though, regardless of what's wrong. The
exception is if you can use your state's lemon law. Keep your service
slips and find out how many attempts your law says they must be given
to fix the problem. The manufacturer usually also gets one try after
that. If, after about 5 tries to fix it, it still leaks, file the
lemon law complaint with your local authority. Make damn sure they
write up a service slip and put it in their system each time they
"service" the car. If it isn't officially documented, it was never
there.