Well yes and no, it really depends on the amount of tinkering you have to do with the vehicle. The best type of vehicle to use is one
with the old style carburettor. It is the easiest because you have a screw to adjust not a computer setting. Most vehicles now have fuel injection and the on-board computer. This is set to pump a curtain amount of fuel for the speed of the motor. Adding a HHO cell will increase the burn ratio but if you don’t modify the computer settings it will still use the same amount of fuel in the same amount of time. If you want to save on gas get in to the habit to check your air pressure every time you fuel up that always works.
Stan Myers did have a car that ran on 100% water back in 1996-1998. he has also patented his designs. he likened the process to an opera singer breaking a wine glass. if you hit the right frequency the glass will shatter. he said it was the same for water, and the frequency he was using was 42800 hz. Instead of sound waves it was electrical pulses in the water. the frequency he refers to is in the microwave spectrum. funny that it is close the the frequency of your microwave oven also. maybe he was on to something.
Midtech Energy is now producing HHO Generators to add to your vehicles intake to help improve gas mileage. Here is a bit on how they work.The HHO Generator sends an electric charge through a liquid electrolyte comprised of distilled or tap water and potassium Hydroxide (KOH), which causes the hydrogen molecules to separate from the oxygen molecules in the water. It then captures the pure hydrogen and oxygen and transports the 2 gases (HHO) into the engine via the air intake system.