Magnas shit their gearboxes 150-200kms in...
Not sure if viable, but adding input anyway - got 6.6L/100km out of mums E39 1996 BMW 528i sitting on 100kmh, ac and radio on... (Sits on 1600rpm @ 100kmh) Love the autobahn gearing lol.
Just get a falcodore though, cheap to run, cheap to service, cheap parts, comfy..