V6 econo run!

[cc]

On a recent trip Bris to Sydney. With a tank full of BP 98 octane in Brisbane 7am, drove south at about 90-95km/hr and 2,500rpm on a warm day and filled up again at the BP outside Pt Macquarie.
Adding 42.08L for 545km travelled at 7.72L/100km or 36.59mpg!
The owners manual predicts 8.6L/100km
So this is a 10% improvement on the book.
Hope its due to the low speed and the engine not running lean.
Still yet to fix the alternator; pretty sure its the root cause of the electrical issues. That is the brushes are on the way out so that when the radiator fans come on the alternator cant respond with more/enough power and voltage level sensitive components go unstable.
Its an oldie but a goodie cause. Pre ecu's and elec fuel pumps, radiator fans and multiple coils. It was the go to check if the car had an elec issue. A solution overlooked these days? Have read brushes are good for approx 200,000km.