how to make car run on water

[SanJohnny]

It is not practically possible to make a standard gasoline car run solely on water. While the concept of using water as fuel is appealing, the science behind it is often misunderstood. Water itself is not a fuel; it is an already-oxidized compound (H₂O). To extract energy from it, you must first break the water molecules apart into hydrogen and oxygen through a process called electrolysis, which requires a significant amount of electrical energy—often more than you would get back by burning the hydrogen. Kits claiming to retrofit cars with "water fuel" systems typically produce a small amount of hydrogen on-demand (HHO gas) to supplement gasoline, aiming to improve combustion efficiency. However, credible studies from organizations like the U.S. Department of Energy have found that these systems do not deliver meaningful improvements in fuel economy or performance and can potentially damage your engine.

The only viable way to power a vehicle with water's core element, hydrogen, is with a hydrogen fuel cell vehicle (FCEV). These are highly advanced, factory-built machines like the Toyota Mirai or Hyundai Nexo. They use pressurized hydrogen gas stored in tanks, which reacts with oxygen in the fuel cell to generate electricity, powering the motor. The only emission is pure water vapor. This is fundamentally different from trying to pour tap water into a conventional car's engine.

Aspect	Conventional Gasoline Car with "HHO Kit"	Factory-Built Hydrogen Fuel Cell Vehicle (FCEV)
Primary Fuel	Gasoline, with HHO as a minor supplement	Compressed Hydrogen Gas
Water's Role	Source for small-scale, energy-intensive HHO production	The emission (output), not the fuel (input)
Energy Efficiency	Net energy loss; electrolysis consumes more power than HHO provides	High efficiency (around 60% in converting hydrogen to power)
Emissions	Still produces significant CO₂ from burning gasoline	Zero tailpipe emissions; only water vapor
Technical Maturity	Aftermarket kits are unproven and can void engine warranty	Advanced, manufacturer-supported technology
Infrastructure	DIY installation; no dedicated infrastructure	Requires specialized hydrogen refueling stations

Attempting a DIY water-to-fuel conversion is not recommended. The risks, including potential engine damage, voided warranties, and fire hazards, far outweigh any unproven benefits. For those seeking alternative energy vehicles, proven options like battery electric vehicles (BEVs) or commercial FCEVs are the only scientifically and commercially sound paths.

[SanMaci]

Look, I messed around with one of those HHO generator kits a few years back. The idea of running my truck on less gas was tempting. I followed the instructions, hooked up the electrolyzer to the battery, and ran a line into the air intake. Honestly, I might have seen a half-mile-per-gallon difference, but it was so small it could've just been how I was driving that week. What I did get was a worried feeling about the extra strain on my electrical system and a weird smell under the hood. I took it out after a month. It's more hassle than it's worth.

[VonLeila]

From a chemistry standpoint, water is the "ash" left over from hydrogen combustion. Re-burning ash isn't feasible. The energy required to split water molecules via electrolysis always exceeds the energy you get from recombining them. This basic law of thermodynamics makes a water-powered car impossible. True hydrogen vehicles, like fuel cell cars, cleverly bypass this by storing pre-made hydrogen, using the car not as a power plant but as an efficient energy converter. The water is the result, not the source.

[DiJameson]

Be very skeptical of online videos showing cars running on water. These are often elaborate hoaxes. A common trick involves hiding a separate fuel source, like a compressed gas cylinder, to actually run the engine while using water for show. These scams prey on people's desires for cheap fuel and energy independence. Investing in such a "miracle" device will almost certainly result in losing your money and potentially damaging your car's engine. It's a classic too-good-to-be-true scenario.