Fuel saving device

Since the development of the internal combustion engine, people have looked for ways to increase its efficiency, in order to increase the fuel economy of the automobile.

Although many technologies have had a beneficial effect on vehicles' fuel economies, claims as to the efficacy of some devices have clearly been bogus or misleading.

An early example of a "fuel saving gadget" sold with claims that were difficult to justify is the 200 mpg carburettor designed by Canadian inventor Charles Nelson Pogue.

A good thing to keep in mind when examining fuel saving devices is that most of these claim major increases in combustion efficiency, something that sounds attractive when you consider the average gasoline engine rarely exceeds 35% efficiency. However, the weak point of the engine is not converting the fuel into heat, but the heat into mechanical energy, hence the reason why many fuel saving devices don't work as claimed. On modern engines there is relatively little scope for improving combustion efficiency. Most of what can be legitimately achieved is done by reducing parasitic losses of accessories e.g. fans, water pump, and pumping losses by taller vehicle gearing.

One reason that ineffective fuel saving gadgets have had some success in the marketplace is that it is surprisingly difficult to measure the fuel economy of a vehicle. This is because of the high level of variance in the fuel economy of a vehicle under normal driving conditions. Consequently, it is extremely difficult to measure small changes to fuel economy.

The large degree of fuel economy variance means that due to psychological factors of selective perception, consumers can be mislead as to the effectiveness of a device.

For this reason, regulatory bodies have developed standardised drive cycles that are useful for statistically significant comparisons of fuel economy.

Vehicle Design Technologies

It is both easier and far more cost effective to design a vehicle to be fuel efficient than to modify an existing vehicle to improve its fuel economy.

Some effective technologies that can improve the fuel economy of an internal combustion engine vehicle include Fuel injection, Continuously variable transmission, Electrical motor assistance (known as hybrid vehicles), variable displacement, technologies to reduce vehicle weight, various friction reducing measures, and vehicle shell designs that reduce aerodynamic resistance (this doesn't improve engine efficiency, but reduces engine power needed to overcome drag, and consequently fuel consumption).

A more comprehensive list can be found in the category Engine technology.

Retrofit devices

Main article: Aftermarket fuel economy device

There are many devices currently being sold as "fuel saving devices" that have negligible or even harmful effects on fuel economy. The US environmental protection agency has issued reports on a number of aftermarket devices that claim to improve fuel economy.

Some of these devices include:

Fuel additives

Materials which are added to the fuel include tin, magnesium and platinum compounds. The claimed purpose of these devices is generally to improve the energy density of the fuel by virtue of the materials added. Acetone is another additive, but may dissolve plastic parts in the fuel system.

These should not be confused with fuel system and valve cleaner additives which remove contaminants from the fuel system and/or remove deposits on intake valves.

Magnets attached to fuel lines have been claimed to improve fuel economy by aligning fuel molecules, but it has been proven by Mythbusters that it does not cause any noticeable changes to fuel economy.

Vapour transfer devices

Various devices claim to improve fuel efficiency by changing the way that liquid fuel converts to fuel vapour. These include "Swirlers" to increase turbulence in the intake manifold and heaters.

Friction reducing measures

Reducing friction is undoubtedly a powerful tool in reducing fuel consumption. Hardened silica tyres have lower rolling resistance than standard rubber tyres.

The typical lubricating oil used in engines has decreased in viscosity over the years. However, using a lubricant with lower viscosity than the lubricant specified by a vehicle manufacturer may damage an engine.

Trip Computers

Many people use devices to monitor their fuel economy. Some vehicles have built in trip computers but many vehicles are not equipped with them. Devices such as the ScanGauge or DashDyno SPD can be used to monitor trip data along with other variables in order to save fuel.

MythBusters

The popular U.S. television show MythBusters investigated several fuel-saving devices using both fuel-injected cars and diesel powered cars under very controlled circumstances.

The concept of fuel line magnets, which supposedly align the fuel molecules so they burn better, was tested and they determined it made no difference in the rate of fuel consumption. They also tested the idea that adding a small amount of acetone to gasoline increases fuel efficiency by making the gasoline burn more completely (presumably without damaging the plastic parts of the fuel system.) However, the result was that alhough there was no apparent damage the fuel system, the efficiency of the fuel actually decreased.

They also tested the theory that a diesel-powered car can run on hydrogen gas alone, which surprisingly, was confirmed as viable, although hydrogen gas itself is very expensive. They also tested a device that supposedly produces sufficient hydrogen to power a car by running an electric current through water (which causes its molecules to split into hydrogen and oxygen). Although some hydrogen was produced, the amount was minuscule compared to the quantity necessary to run a car for even a few seconds.

The show also tested a carburetor that, according to its manufacturer, could improve fuel efficiency to 300 miles per gallon. However, the device actually made the car less fuel efficient.

They also determined that a diesel-powered car can run on used cooking oil though they did not check whether it damaged the engine.

The show noted that out of 104 fuel efficiency devices tested by the EPA, only seven showed any improvement in efficiency, and even then, the improvement was never more than six percent. The show also noted that if any of the devices they tested actually worked to the extent they were supposed to, the episode would have been one of the most legendary hours of television. The show also cited common sense by stating that if there really was a device that dramatically increased fuel efficiency, it would certainly be common knowledge.

See also

• history of perpetual motion machines
• Corporate Average Fuel Economy
• Emission standard

External links

• Vehicle Fuel Economy Gauge measure instant and average MPG on all 1996 and newer vehicles.
• US EPA's report on fuel saving devices
• Tony's Guide to Fuel Saving Gadgets including a case study on Vaporate
• FCIC warning on fuel saving devices
• Better Business Bureau list of ineffective retrofit devices and glossary of terms.
• Monitor Driving Habits shows how to use a trip computer to save fuel.
• Reduced Fuel Consumption Device - How it works.