The EPA has been testing
such devices since the early 1970s - both because of a desire to save fuel, and equally because many such devices
actually make emissions worse. The EPA guidelines clearly explain what must be done to properly evaluate a fuel
"saving" device, and in particular make it absolutely clear that emissions measurements on the Inspection &
Maintenance test (the equivalent to the UK MoT) are of no value in this evaluation. The essential requirements to prove
a fuel "saving" device works are:
- rolling-road tests, over standard cold-start cycles such as the FTP75 (US) or ECE+EUDC (Europe)
- a test car (preferably two) that is reasonably modern, and in good condition (emissions and economy in line
with when it was new)
- at least two tests in "standard" condition, followed by at least two with the device fitted (to assess statistical
variability)
- ideally, a final pair of tests with the device removed again (to prove it was the device that made the difference,
and not some underlying factor such as components bedding-in)
A device that has test data conforming to these requirements, and where the gain is several times larger than the
test-to-test variability, is almost certainly of genuine benefit. Anything less rigorous (old car, no repeat tests, etc)
should be treated with some suspicion.
Many American devices claim "We have a CARB number and so it is legal to fit this device". While true,
this does not in any way indicate that CARB (California Air Resources Board) certify that the device actually offers the
benefits claimed. The CARB number merely indicates that CARB do not believe the device makes emissions worse, and
does not indicate anything else. For example, the CARB Executive Order for the
Tornado Fuel Saver specifically states:
This executive order does not constitute a certification, accreditation, approval, or any other type of
endorsement by the Air Resources Board of any claims...concerning anti-pollution benefits or any alleged benefits.
Since the vast majority of fuel "saving" devices have no effect at all, either positive or negative, it is unsurprising
that they can obtain CARB numbers (and in many cases this is based on "engineering judegment" rather than actual tests).
To check if a particular device has a CARB number, visit their
database.
People frequently ask why I criticise such devices without having personally tested them. The reason is that I
could fit one to my car but it would prove absolutely nothing. Any fuel economy effect would be lost in
the variation of normal driving (as discussed here). The emissions tests I could do
(basically CO and HC at idle, as measured on the MoT test) would say nothing at all about the effect on overall emissions
while driving, and hence environmental impact. Proper performance testing would require multiple rolling-road tests with
and without the device, which would be expensive and time-consuming. For these reasons, I also believe the customer
testimonials often quoted by makers of such devices to be of little value.
Often these devices claim to alter the combustion process in some way. Even assuming that this were possible,
remember that the engine has been optimised for the "normal" combustion. To get any benefit from this
"altered" combustion you would need to change fuel delivery, ignition timing or even the design of the cylinder
head to suit! Diesel combustion is a lot more efficient than petrol combustion, but you can't just fill up
your petrol car with diesel and expect a 20% economy improvement (no, don't even think about trying it -
it will be very expensive to repair!)
A typical claim is that the combustion with the device fitted is somehow "better" or "more complete". There is
never however any detail as to what is meant by this. And it is a firmly established engineering fact that,
on any reasonably modern engine under normal operating conditions, the burn is already at least 98%
complete. The unburnt fuel in the exhaust (even before the cat) represents 1 or 2% at most
of the input fuel. If you factor in the energy in the CO emissions, the figure still only rises to 3% maximum. So even if
the fuel "saving" device could totally eliminate unburnt fuel and CO in the exhaust, and give an absolutely 100%
complete burn, you would only save 3% of fuel. Claims that 10%, 20% or even more of the fuel is not burnt and escapes
into the exhaust are entirely false - the unburnt fuel figure is higher when the engine is stone-cold, and
at high load and speed conditions, but since the engine only spends a small fraction of its time under these
conditions their contribution to overall fuel consumption is small.
(NB That is not to say that the overall efficiency of a modern engine is close to 100%. There are losses due to
the fundamental nature of the engine cycle (the "Carnot cycle"), which limit even theoretical efficiency to about
40%, and there are also losses due to friction, heat loss to the walls of the cylinder and the piston, "pumping
loss" due to sucking air past the partially-open throttle blade, etc. These losses are however well understood
and the gains to be had from various technological changes are accurately known.)
The other reason why these devices can't work is simple business. Fuel consumption is a very hot
topic in the European car industry at the moment, because it is directly related to carbon dioxide,
which is a "greenhouse gas". Consumers and legislators are demanding ever-better fuel consumption
from new cars. The industry is investing literally billions of pounds on more efficient engines,
for example diesels (and we wouldn't do that if we were in the pay of oil companies,
would we?) But these more efficient engines are also much more expensive to make - for example a diesel will produce
about 15 - 20% less carbon dioxide, but adds about £500 - £1000 to the cost of a car. These "fuel
saving devices" claim nearly as much benefit for a tenth of the cost - the car industry would not only
sell its grandmother for this kind of saving, but sacrifice its first-born son too!
Given that, you have to ask why any such device isn't fitted to new cars as standard. The answer is
simple - industry believes they are of no significant benefit. Otherwise, they would be on new cars. No question.
The car industry has seen hundreds of these things go by, and can't afford to waste thousands of pounds on testing
each and every one of them. But if you'd invented a miracle gismo like this and knew it worked, wouldn't
you pay your own money on tests to prove it, given that you could then sell millions?
Some people argue that car makers are so keen to reduce costs that even the few pounds that one of these devices
costs would be too expensive. And of course on some entry-level cars, and in cheap-gasoline America, there is
some truth in that. But in Europe (especially in the UK with CO2-based company car tax) many consumers have proved
willing to spend several hundred pounds more on a car if it is more economical. You need only look at the booming
sales of diesels, which cost anything up to £1000 more than the petrol equivalent, for proof of this. There is
a clear profit incentive for car makers to equip at least part of their range with more economical engines and
so the potential market for a genuine fuel saving device runs into tens of millions of pounds a year.
Sufficient incentive for any manufacturer of such a device to spend a few thousand on tests, you would think.
Exactly the same argument applies to the claims of increased performance made by many makers of such devices.
For some car makers, even just one or two percent more horsepower is worth thousands of pounds. If a cheap and
simple device like a magnet, air bleed, fuel "catalyst" or turbulence increaser could really give 5 - 10% more
power, would they not be fitted as standard on most BMWs, Porsches, Ferraris, etc?
I have worked for or with some of the world's biggest car makers and component suppliers, and nobody I have
spoken to in the industry has ever regarded these fuel "saving" devices as anything other than a con. They
are never advertised in the journals aimed at engineers within the new car industry, the makers never
present results at trade conferences, and no serious books on the subject (of which I have read dozens) even
give them a mention. Certainly you don't find car engine designers saying to each other, "If only we could fit
(device x) to our engine, but (company y) has got the patent on it". Even at normal market price these devices
are allegedly massively more cost-effective than any known fuel-saving technology. Arguments about the difficulty
of fitting them to new cars do not wash either, since current cars contain extremely complex devices that only
a few years ago would have been considered impossibly difficult; the car industry has a good record of solving
such problems.
You may well wonder, if these things don't do what they claim, why are the makers not prosecuted by (in the UK)
Trading Standards or the Advertising Standards Authority? The answer is that many are, but it is difficult and
expensive to prove the device doesn't work. The device usually then simply pops up again under a
slightly different name claiming some slightly different technical features. For devices sold in the UK, it
is however well worth while searching the
ASA
website, just in case. Remember that the ASA is effectively funded by the advertising industry, so does
not make judgements against advertisers without good reason.
Several such devices proudly state that they are "award-winning!", to which I have just one comment:
so were Milli Vanilli...
One more thing to remember is that thousands of scientists and engineers all over the world have been
working on car engines for decades. The physics of engines is pretty well known now and you have to
ask yourself if some amazing new breakthrough, only involving bolting something to the outside of
your engine, would really have escaped the car industry's notice all that time.
The following pages give some more information on the types of "fuel saving device" you see advertised,
and why they can't work as described (note that some devices claim more than one effect). I can't list every
device on the market, because there are literally hundreds of them - in many cases the identical device sold under
multiple names. Even if the device you're looking at isn't specifically listed, it almost certainly falls into
one of these catagories:
Magnets round the fuel line or in the air flow (Ecoflow, FuelMAX, FuelSaverPro, etc)
Catalysts in the fuel line or tank (Broquet, Fitch Fuel Catalyst, Prozone, etc)
Platinum-based combustion enhancers (PVI, Gasaver, Ctech3000, etc)
Ignition enhancers (Fuel Saving & Power Push, Fireball Ignition, etc)
Air bleed into the inlet manifold (Ecotek, Khaos, Powerjet USA, etc)
Turbulence increasers (Ecotek, Tornado Fuel Saver, Powerjet USA, SpiralMax, etc)
Devices to "atomise the fuel better" (Ecotek, Tornado, SpiralMax, Vaporate, etc)
Oil additives (Slick 50, Duralube, etc)
Fuel additives to enhance combustion (Acetone, PowerPill, BioPerformance, etc)
Engine "cleaning" products (10k Boost, Powerboost, etc)
Electrical modifications (grounding straps, voltage stabilisers, etc)
Hydrogen generators
Some background:
