Ford I believe use Valvoline, Would recommend you try Caltex Havoline Energy 5w -30 It is a group 3 oil base, check out the caltex website, www.caltex.com.au.
"go to motor oil area" will give you 50+K's per tank.
Have tried Shell 5w-30, and 5w-40 claimed synthetic, Ferrari oil.
This is not a true synthetic. All there oils are good but not as good as Caltex Energy.
Have not looked at Fuchs oil, you would have to ensure that you use a 5w-30 or 10w-30 grade of oil.
Check out tyre pressure, and on long trip engage cruise if you have it.
Best mileage I received prior to Headers, filter, bigger snorkel etc was 650 per tank, now out to 840 on highway included using 5w-30 Caltex Energy, Halvoline in USA have been the first to introduce a Ilsac 3, oil not in Australia yet current oil is Ilsac 2.
Around town expect around 560-600 K's.
The AUxr6hp is fitted with a standard forte exhaust system, not a
sport system, can improve by fitting 2.5" system from cat back without headers.