We have the moon wheels already under trial.... Results are minimal at best on our current rigs... But that may be due to not enough supporting aero...
The trailers boat tails we can't use in Australia as we go over length by adding it on unfortunately
In relation vortex generators... Most of the vortex strikes seem to be a thing of the past.. With products causing twin closed vortices being used now... Eg airtab is one brand... We have them in use and can notice some mileage saving just when installed on last trailer... But I am still to trial on all the locations on the tractor and between trailer gaps etc... Once I find a decent supplier we will progress.
Other aero like replacement hoods to upgrade old poor aero designs from the manufacturer.. Aero mirrors.. Etc.. Still to be actioned as well.
Parasitic losses to the engine I am also starting to investigate... Things like the mechanically driven fan... And other things need to be rectified.. But it's a big work in progress...
I am also investigating tilting the radiator back with a electric fan behind it to reshape the aero of the front...
We can't use undertrays due to amount of wildlife.. (damn kangaroo's) so I can rule that out as well...