vy ecotec sump plug

[wortus]

I'd be buying one of those ring spanners designed to remove rounded nuts. They look something lime this image and work by putting the force onto the centre of the flat faces on the nut not the ends.
Go and buy one from Holden with the correct washer and tighten it up with a torque wrench to the required torque, using a new washer each oil change. This is what I do and I have never had one come loose or be that tight I needed to use a bar on the end of a spanner.
To get my sump plug out I use a ring spanner and place one hand over the nut so the spanner doe snot come off the nut rounding it. Sockets are not a good idea use a ring spanner and hold it onto the nut.

 

[Interloper94]

Sockets are fine, just gotta make sure to hold it on there and not let it slip.

 

[gossie]

Sockets are fine, just gotta make sure to hold it on there and not let it slip.

And the correct size.

 

[malmensa]

A 6 point impact socket on a heavy breaker bar should do the trick.

 

[thomoKW]

M24 x 1.5
For anyone landing here. Thread about 10-11mm deep. Nut 19mm.

fits my VY series 2 L67

tridon TDP038

The Al washer is 29 mm OD x 24.2 ID