I have tried a GF chip on a Ford Aerostar 4.0L 6 Cyl. 2WD just for testing purpose I found no increase in mileage nor HP. This Aerostar has 184,000 km/130,000 miles. The chip is installed at the IAT (Intake Air Temperature Sensor).
Then I tried an Hydrogen Generator (produces brown gas) on this Ford Aerostar 4.0L and got about 31% increase in mileage. (7.1Km/L to 9.4Km/L) I am still testing during this winter how it stands up against -25C. So far it didn't freeze on me. This Hydrogen Generator is easy to install and uses Distilled water Potassium Hydroxide mix (wintertime adds 1/10 Isopropyl Alcohol The mfg. claims 45% increase but then I think I have to install a EFI regulator in order to gain that. My trips are usual highway and return trip is usually windy. Inspected the intake and exhaust valves after 10,000 km/6300 miles and they are as clean as it can be. My next test will be an 6.0L V8 in a truck as they have more room to install the unit. I am telling you on the 10,000 km I haven't used the 1 gallon mix yet.
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ALJO 'Forever Young @ Heart' provide on their travels Music Entertainment to Senior Care Homes