My diesel Transit van used to do somewhere between 25 and 30mpg. I have done four test fill-ups, three with the gizmo operational and one without. My average consumption is currently 34.58 mpg, which includes a run to Cornwall, another to Exeter, some short, local journeys and up through the lanes to Dartmeet. The best mpg has been about 37.06mpg. I then disabled the gizmo and calculated 27.47mpg including a run to Exeter and local journeys. Basically I put in £20 worth of fuel and did 117 miles with the hydro kit, but only 87 miles without it. That’s like gaining an extra gallon of fuel, or an extra 30 miles of driving, every £20. That’s quite a significant improvement, and won’t take all that long to get my £250 back (even without considering the emission reduction side of it). Dearbhaile has had one fitted to her more modern car and can read her fuel consumption from the dashboard: 36.8mpg on the way down to Paignton, and 50mpg on the way back.
To read more about it, see my previous post (click the ‘Energy’ category, or just scroll down, or visit the De Verde website).