Can a diesel engine run on water?

The answer is YES! The diesel engine can’t run entirely on water but injecting water gives the engine a denser charge on compression giving the engine more compression and more horsepower. We have been running water injection for a couple of years with no downsides. On our Duramax 6.6L we are picking up approximately another 1.5 more miles to the gallon on the highway. With the Jetta TDI we are picking up another 1.5 miles to the gallon highway. We expect to pick up more when the water injection system is upgraded to include vaporization.