When towing a caravan with the 6 speed Aisin trans the converter lock will not stay on until over 1800 rpm in 5th that is over 100 kph under 1800 rpm the lock is on and off and the trans changes from 4th to 5th and 6th and back again several times a minute at times. Tis adds 4 to 5 litres per hundred to fuel consumption compared to the previous 5 speed model. If the trans was reprogrammed to lock converter when manual mode is selected you could tow at engine speeds above 1600 rpm approx 90 kph locked and save trans from gear and lock shifting continuously. This could help trans life also help fuel usage savings as you could travel slightly slower which reduces wind resistance of caravan if you select D the trans spends most of the time in 4th gear changing up at times. If slight head winds are present trans stays in 4th gear all the time and returns upwards of 20 lph again if you could lock the converter and travel a bit slower chances are the car would be happy and a reasonable fuel usage of around 14/15 lph could probably be achieved.