Darwin Adelaide trip

Not long after my Chiptorque exede was fitted to my gen2 3 I did a Darwin Adelaide. It also has a full 3'' stainless. After the 500km from Tennant Creek to Alice springs the trip computer told me I had only 50km to empty and the fuel light was on, but upon refueling there was still a bit over 20lt still in the tank, enough for a nother 200km. Even though I was sitting on the 130kph limit. The fact you can set the cruise control for 130kph and not touch it for 500kms and a good dyno tuner is probably the answer for good economy. Once in SA on cruise at 110 my trip computer was showing an economy of high 7s. New in September 09 now has done 24000km