Fuel-saving device


Fuel-saving device, n.m. :
An accessory device and/or a consumable which allows to decrease the consumption of fuel of an existing heat engine for an identical usage.

The accessory character of the fuel-saving device and its simplicity make it an interesting solution to improve what exists.

It holds no connection to the good practices of the user regarding:
- the driving of the engine
- its maintenance and the maintenance of its peripheral devices
The Mathis VL 333 used only 3 liters each 100 km in 1946, an intelligent concept including all the fuel saving techniques available after WWII. Made in France.
Mathis 333 VL of 1946
3-wheeler, 3 people, 3 liters per 100 km.

It should be reasonably easy to install not to enter into the category of a significant alteration, as described in administrative terminology, which modifies the conception of the engine. When made a standard equipment, it becomes an innovation and should be described as part of the performance of the manufacturer.

Processes used to decrease the consumption

Antistatic treatment of the fuel

The aim is to remove the static charges accumulated by the fuel which, by landing up on the droplets, attract the droplets to the wall of the cylinder. The mix becomes less homogeneous and does not burn as well. Antistatic agents (for example STADIS ® 425) are used in fuels and solvents to disperse the static electricity. We have all seen unsightly antistatic black rubber bands rubbing the rears of cars. Another technique is to trap the static charges by diverting them with a magnetic field, just before the engine.

Water Enhancement

Simply adding water allows to improve the quality of the combustion. Water is an indispensable catalyst in most chemical reactions which, without dampness, see their kinetics vary in a considerable way. In the presence of heavy hydrocarbon and in some conditions, water produces a cracking into lighter elements of which combustion becomes easier than that of the initial types found in the engine cylinder. Water also has a direct thermodynamic impact on combustion due to the enthalpies of phase change (latent heat).
Water can either be mixed to intake air or to the fuel (aquazole).
NEVER mix water and fuel yourself! You would break your engine.
The industrial cousin of water enhancement is called "wet-ashing oxidation" and the process is used in the treatment of aqueous waste.

Addition of catalysed damp air to the air intake

The technique improves the performance of water enhancement. A catalytic reactor heated by the exhaust gases improves the physicochemical reactions in the presence of water and air, which would not have happened in the case of a direct intake.

Injection of water-alcohol

In diesel engines, injection of a water-alcohol mixture (sometimes called aquaol) really consists in producing an alcohol bi-fuelling. But the presence of water also acts on combustion and improves performance. Compressing a tank which contains a water-alcohol mixture with the pressure of the turbo and injecting it with a very fine nozzle after the turbo is sufficient. Without any specific tuning, the system is only triggered when the engine is under load.

Addition of Brown gas to the air intake

Brown gas, also called HHO, is a monatomic mixture of hydrogen and oxygen in a gaseous state. It is produced by the pulsed electrolysis of an aqueous electrolyte (water and potassium hydroxide for instance). Its molar volume is twice that of the dihydrogen and dioxygen mixture obtained by means of a classic electrolysis. Mixed with the air intake, it quickly recombines to water at the beginning of the combustion of the gas volume, producing its known effects. The current intake from the alternator should not be too high, as it would then produce the reverse effect.

Body aerodynamics

Adding a deflector or taking the carrier bars off the roof are well known solutions. Other exists, such as the implementation of vanes at the rear of the vehicle (a rather ugly solution) to optimise the path of the boundary layer. The surface state of the body of the car also plays a role, which is difficult to assess or to master, however.

Aerodynamics of the intake circuit

The path of the air between the filter and the engine should be made easy to minimise frictional losses. Replacing the piping may bring an improvement, therefore. If the air intake is located at the front of the car, dynamic pressure of the relative wind also plays a role and improves the filling rate. In the case of "petrol" engines, having the air intake rotate after its carburisation improves carburisation by a brewing process, but this should not slow down the air beyond a certain threshold.


An intercooler is an air-to-air or air-to-water exchanger which allows to cool the air intake (whether carburated or not) and to improve the filling rate. Output is increased and consumption is reduced. Added to an old engine, this works as a fuel-saving device.

Turbo charger

The turbo compresses the air intake to increase the filling rate by using the speed of exhaust gases as a source of energy. As is the case with the intercooler, this can be considered a fuel-saving device when added to an old engine, what is not easy to achieve.

Improvement of carburettors

Many devices have been invented and commercialised to improve carburettors:
- richness correction device
- turbulators to improve the mixture
- water injectors
We believe that special carburettors (of which there is a long list) are not true fuel-saving devices as everything needs to be changed.

Recycling of the fuel vapours

On modern petrol vehicles, the "canister" device fills this function. Collector's cars would highly benefit from such an equipment, even without a true canister.

Electronic microchips

Changing the microchip of a calculator is similar to changing the programme which manages the fuel injection (cartography). On some engines of a single series, manufacturers offer several powers simply by implementing different programmes. It is easy to understand that an optimisation is possible and that, in some cases, consumption can be reduced.


Using bio-fuels does not allow to reduce fuel consumption per se, but it does limit the consumption of fossil fuels. Vegetal oil or bio-ethanol can be mentioned, but they have the counter effect of monopolising agriculture for other objectives than food. Gasifier synthesized water gas is more eco-friendly, but calls for an irreproachable organisation. Recycled oils, mixed to diesel oil in small proportions, are a very good recycling chain. Bio-gas produced by methanisation of waste would be ideal, but it happens to be extremely corrosive for engines.

Usage of gas or of bio-gas in diesel engines

The process consists in letting the injection pump in idle position while accelerating the engine and mixing gas (propane, butane, bio-gas and so forth) with the air intake. The economical result is better in certain conditions. The process holds its place on this page, therefore, as a faraway cousin.

Improvement of ignition

In the case of "petrol" positive-ignition engines, this is a crucial factor. The second spark plug of plane engines works as a fuel-saving device if one considers that it secures the spark. Electronic ignition on an old vehicle has a spectacular effect and should be the first investment one makes on a collector's car which is not equipped. Such ignition devices now take advantage of the flexibility of electronic, which allows multiple configurations.
Usage of spark plugs with built-in capacitors also offers an appreciated benefit by a considerable improvement of the quality of the spark.

Oil additives

Several serious additives exist, which improve lubrication in a significant way, but a consumption decrease of 5% is seldom exceeded.

Fine filtering of engine oil

Usage of a small pore size filter on the oil circuit considerably reduces the wear of the engine and hence preserves compression rate and original consumption in the long term. Such a filter also allows to increase intervals between oil-changes and to generate supplementary savings.

Fuel additives

A standard offer from major manufacturers, such additives have certain virtues and significantly increase the quality of fuel, while "cleaning " the circuit. Whether their high price compensates for the resulting savings is another question. Calculations should be left to each specific case. Some recommend to add a small percentage of acetone in the fuel, but we do not hold usable data on the subject. A trick of mechanics on collector's cars is to add 2% diesel in the unleaded fuel. For its part, isopropylic alcohol allows to emulsify water condensed in the fuel and avoids many problems.

Solar Hybridisation

An interesting solution for cars staying in the sun is the equipment of a photovoltaic panel, but it is difficult to carry out. Storing electricity in a battery allows to reuse the energy through:
- an electric engine inserted in the non-driving wheels
- a Brown HHO gas generator or classic electrolysers.
The energy is free and the consumption savings are real.

GEET Pantone

The "Pantone engine" is not a fuel-saving device. It is a fully fledged carburizing process which is meant to replace a classic carburettor of a petrol engine. A mixture of heavy hydrocarbon, water and air is sucked into a reactor heated by the exhaust gases. A reaction called "reforming" then occurs (with or without pre-oxidation), which produces light hydrocarbon, of which combustion is much easier. The Gillier-Pantone variation is still relatively complicated but is an accessory meant for diesel engines which falls in the "fuel-saving devices " category.

Good practices of the user

Driving of the engine

Some simple rules allow to decrease consumption:.

Let us remember that fuel delivers a power (force multiplied by speed) through the engine, power meant to:
- accelerate
- go up-hill
- fight against the friction of wheels and air, more or less proportional to the square of the velocity.

It can henceforth be deducted that accelerations should be reduced (while taking the range of better performance into consideration) and that one should:
- accelerate slowly when entering a highway
- try not to use the brakes, such a behavioural trick calling for some forward thinking on speed changes, by looking far ahead
- avoid entering into races
- keep a constant speed in general.

It can also be deducted that hilly roads should be avoided (difficult to achieve in a mountain environment)
- As one always goes down at one point, use the slope, without giving up safety.
- The lighter the load, the lesser the consumption ; think about unloading those cement bags from the trunk!

It can lastly be deducted that friction is an important factor, and that one should:
- drive more slowly
- have well inflated tyres
- ahave a clean car
- avoid carrier bars, open windows, antennas, and so forth.

With a modern car, it is better to remain engaged when going downhill or decelerating as the calculator is going to cut the fuel. When declutching there will be some consumption to keep the idle position. On older vehicles ,the cut does not occur and it is then better to declutch, while remaining very alert as the engine brake is not active any more. Always be ready to clutch and brake.


A well maintained device has a reduced consumption and pollution:
- clean air filter
- regular oil-changes with a quality oil, if possible with a change of filter each time.
- well inflated tyres
- controlled parallelism
- quality fuel
- regular cleaning of the fuel circuit by a specialist (flexible and injector)
- during Winter, let the engine warm up for a few minutes, if possible when the vehicle is stopped.

French links (sorry)

- Arrêté du 26 février 1976 relatif aux dispositifs antipollution et aux dispositifs économiseurs de carburant destinés à être installés sur les véhicules en service (Legifrance.gouv.fr)
- Reflexion sur l'energétique des véhicules routiers (11,5 Mo) par l'association Inter Action à Strasbourg.
- Le moteur à eau (3,26 Mo) sur www.hydroretro.net