The fuel device was given to me to test on a mechanical engine diesel or petrol either one didn't matter. So in the past weeks we have been testing this fuel saver device and had some luck with our results. We put the device on a Nissan Patrol 4.2L non-turbo diesel ute. In our tests we have given engine out and work how it suppose to. The ute does 1100 km's without the device and now gets an average of a 15% better fuel range with the fuel device. The engine runs smoother, at idle and has a better top end. It blows less smoke on take offs as well.