so far, it works for us. of course, i was sceptical at first. Who wouldnt be! First tried it on a triton V8 Engine Ford E150. It didnt save at first but started saving on the third trip. Almost all our gasoline fed cars we have have one: '86 baby benz or 190E mercedes benz, 97 5 door Suzuki vitara, '97 mazda 626, '90 260E Mercedes Benz, my classic '78 w123 200 Mercedes Benz. My brothers '03 supercharged grand prix already saves by 3 more miles per gallon i think. That would mean 30 more miles per 10 gallons. Same driving conditions and attitude, of course. I believe the problem with the device is the new engines since the computer will detect that the mixture is too lean and will automatically adjust the fuel being fed therefore causing more consumption.