My RB30 GQ is getting about 17.5 litres per hundred too, but it ain't got anywhere near 300 hp...

When I first got it it was totally stock, it used about 13 litres per hundred or thereabouts. I've added a few things like rhino roof rack 2 inch lift, snorkel, second battery, fridge etc, so a bit more weight and wind resistance I suppose.

Off-road on sand with the tyres down at Yeagarup over the Easter break it was more like 29 litres per hundred! I need to repair and fit up my aux tank next to have something approaching range.