I have a
Performance & Economy Diesel Tuning by Tunit - Work, Play & Save fitted on my 2.8JTD Fiat (4.5t max), and I have been 'playing' with the settings for a few months now.
The vehicle came (second hand) with the Tunit box already fitted and set at number 7 (0-9 settings), with this setting I have been getting about 25mpg.
The vehicle has pulled well on the hills and has a good turn of speed when overtaking, but I really wanted to know if this box worked, so I initially set the box to number 9 and set off on a 240 mile trip to south Wales a few months back, however there did not seem to be much difference that I could tell.
The box was set at number 1, and another similar journey recently made it quite clear that there was a distinct lack of torque, on the hills and when overtaking lorries on the motorway.
The box has been set back to number 7, where it shall stay now.
As for fuel consumption, I am not sure, but I did seem to get about an extra 20 miles per tankful, ( I usually get about 300 miles before the fuel light, but with the setting on 1, a further 20+ miles) not really enough to justify the lack of torque, without the box set to a higher setting.