Rumour heard that in the US the oil used is 0W40, but in Oz Holdlen uses 10W50 - additional wear on start up maybe? probably not enough of a difference to explain the consumption, and also wouldn't explain the variation (some cars use none, some use heaps)
Also in the rumour file, apparently, if an owner complains, Holden seal the sump plug and measure consumption between services - I'd be getting some sucked out through the dipstick to get a rebuild
(either that or dumping it on the secondhand market and buying something better engineered - a Hyundai perhaps hahahahahahaha - sorry, couldn't resist)
