The next time you’re filling up your car’s fuel tank, watching the price slowly climb, you may wonder if there is an easy way to save some money on fuel. It turns out there are some great ways to improve your mileage, but using an HHO kit isn’t one. If you are looking into HHO kits to try to improve your car’s mileage, you should know that these kits do little more than try to scam you out of money and they haven’t been proven to work.

In this article, we’ll take a look at why HHO kits don’t work and give you some legitimate ways to improve your mileage and actually start saving a little bit (or a lot) of money on fuel.

In This Article

What Is an HHO Kit?

HHO kits are devices that use water to produce hydrogen and oxygen to add to your vehicle’s fuel. Hydrogen is extremely flammable and while oxygen is not technically combustible, it makes things burn much more rapidly and efficiently. The chemistry behind the process of making these gasses is simple: pass electricity through water and the energy splits the water molecules into its two components, hydrogen and oxygen. This process is known as electrolysis. Most HHO kits use electricity from the vehicle’s alternator, pass it through a water tank, and then collect the gas and add it to the vehicle’s fuel system.

It turns out that some engines actually can run on hydrogen gas. It’s easiest to show that this works with an engine that has a carburetor rather than fuel injection, but you will need a large supply of hydrogen gas (typically from a gas cylinder) in order to demonstrate the process. Fuel injected cars may also run on hydrogen, but the modifications that need to be made are not as straightforward as carbureted engines. The modifications are also fairly dangerous, and the risk of backfire is much greater when running engines off of hydrogen.

Why Don’t HHO Kits Work?

There are several problems with using HHO kits. While the devices might produce hydrogen and oxygen, the amount produced is extremely small. Even if an engine can burn these gasses, the HHO kit won’t create enough of them to matter. Furthermore, the energy that burning these gasses creates is less than the energy that the alternator provides to create the gasses. The electrical drain on the vehicle’s alternator will cost more in fuel than the device will ever produce. This follows the first law of thermodynamics and it can’t be broken.

In fact, most commercial applications of electrolysis — where large factories produce hydrogen and oxygen for use elsewhere, like welding for example — only have efficiency rates of 50% to 60% which means that about half of the energy used to create the oxygen and hydrogen from water is lost in the process.You can expect much lower efficiency rates for smaller units like HHO systems.

Some claim that even the small amount of hydrogen and oxygen that make it to the combustion chamber in your car’s engine improve the mileage by other means. These are dubious claims at best, and most of these changes can be made to your car’s engine even without an HHO kit. For example, it’s possible to improve mileage by “leaning out” the car’s air/fuel mixture — leaning out refers to reducing the supply of fuel going to the engine. In cars with a carburetor, this is as easy as turning a few screws, but in cars with fuel injection, you will need to know how to reprogram your car’s computer or make drastic changes to the emissions control system. This modification will make the engine run hotter, though, and can often burn the valves in your engine as well. Fixing burnt valves is a very expensive repair in most modern cars and will quickly eliminate any savings you made in fuel.

The only way a hydrogen system in your car would save money is if you have a cheap source of electricity elsewhere (like a solar panel array, for example) and you also have all of the equipment to safely capture the gas produced in the electrolysis reaction, transfer it to your vehicle, and add it to the fuel system. We can’t recommend that you try this, especially since the risk of handling dangerous gasses is not worth the marginal mileage gains (if any), let alone the cost of all of the expensive equipment you would need to accomplish this in the first place. Rather than doing something this drastic to improve fuel economy, there are many other things that you can do today, some of which are free, which will improve your mileage.

Free Ways to Improve Fuel Economy

The first thing you can do to improve your mileage is to get rid of anything in your car that you don’t need. If your car is full of trash or things that you don’t use on a daily basis, it takes energy (extra fuel) for your car to move all of that stuff around. Throw out the garbage and remove anything else you don’t need.

Another easy way to get more miles out of a gallon is to change your driving habits. This is as simple as accelerating less quickly from stop signs and traffic lights and slowing down well in advance of places you know you’ll have to stop, allowing your car to coast toward them instead of pumping the brakes. Basically every time you have to use your brakes you are wasting energy, so try to use them as little as possible. Also, if you live in an area with lots of hills try not to accelerate going up the hills. Let gravity help you gain speed on the way back down if you need it.

These two methods alone — carrying less in your car and driving less aggressively — can prevent you from losing 10% to 40% of your fuel economy, and they’re absolutely free. That can go a long way over the course of the year to save you some serious money.

Other Ways to Improve Fuel Economy

Once you try the things mentioned above, there might be other ways to get a little more out of your car’s fuel tank. If your car’s check engine light is on, odds are this is because something in the emissions control system needs attention. A bad oxygen sensor or EGR valve, both parts of a typical emissions control system, can lead your car’s computer to pump more fuel to the engine than it really needs, reducing your mileage unnecessarily. If your check engine light is on, have a qualified mechanic take a look at it and see if it can get fixed.

Additionally, oil leaks, low coolant, and many other things can lead to your car getting poor mileage. Have any oil leaks repaired, especially if your car is making a blue-ish smoke. Make sure you have enough coolant in the radiator, and, in general, make sure your car is running well. A car that runs well will get its best mileage.

If your car is on its last legs and you know you’ll be replacing it soon, a great way to save on fuel is to replace your car with a hybrid or electric car. Nowadays, you can find a used Toyota Prius for only a couple thousand dollars, and these cars are widely regarded as some of the most reliable ever built. The icing on the cake is that they can get up to 45 miles to the gallon, which will certainly save you money on fuel unless you’re driving one already.

Another great option is to buy a car that is fully electric. As long as you don’t take long trips very often, these cars are great for going around town or commuting to the office every day. For example, used Nissan Leafs that are only a few years old can usually be found for around $8,000 and can be charged from a normal electrical outlet at your house or apartment. The range for some of the older Leafs is a little lacking though, at only 70 to 100 miles per charge, but if your commute is less than 40 miles per day these cars are perfect.

At $0.10 per kilowatt-hour (kwh) of electricity and assuming an EPA-rated 30 kwh per 100 miles, the yearly “fuel” cost for a Leaf can be around $360 to drive 12,000 miles, but driving carefully reduces this cost even further. (It may be more or less depending on your local electricity costs.) Compare that to the $1,400 cost to fuel a car that gets 24 mpg at $2.80 a gallon. Additionally, electric vehicles don’t need any maintenance except for new tires, windshield wipers, and brakes. No oil changes, coolant flushes, air filters, fuel injectors, spark plugs, or anything like that. As long as your driving needs aren’t too great, you can save some serious money by going electric.

If you do need more range than a Nissan Leaf can get you, though, some car manufacturers are offering “plug-in” hybrid cars, such as the Hyundai Ioniq or the Toyota Prius Prime. These typically have larger battery packs than a normal hybrid car so that they can drive in “fully electric” mode for around 40 miles. You can charge them at home and drive them like an electric car for the fuel savings, but they have engines in them as well that you can use for longer trips.

In Summary

While the claims of gas mileage improvements from HHO kit vendors seem wonderful, there is not a single one that is proven to work. In fact, it’s impossible, outside of very special situations, to get any real savings out of a device like this due to the laws of thermodynamics. But if you want to save yourself some money in fuel there are some easy ways you can try, like driving less aggressively, fixing your car up, or buying a more fuel-efficient vehicle when the time comes.