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June 01, 2006  |   Comments (0)   |   Post a comment

Too Good to Be True?

An engineering expert takes exception to the promises of better fuel economy, extended oil intervals and reduced emissions made by suppliers of fuel additives, engine attachments and other aftermarket products. The first of a two-part article.

by Dan Herman

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Prominent among the many challenges facing the school bus operator are the factors of fuel economy, maintenance cost, emissions control and fuel quality.

When someone approaches you with a product that promises to provide miraculous improvements in these areas, it is tempting to buy. But are these promises hollow?

This two-part discussion will provide you with questions to ask that will help you determine whether the promises will be met.

Start with the engine
Engines attract entrepreneurs. Since the engine is the prime mover — the source of power in the vehicle — it presents the most obvious place to modify or “improve” the vehicle. Entrepreneurs have filled the marketplace with products claiming to improve the operation of an engine. They fall into two categories: attachments and additives. Attachments may be fuel or oil filters or fuel treatment or modification devices. Additives treat the fuel, lubricating oil and coolant.

The common list of claims includes some or all of the following: reduced exhaust emissions, increased fuel economy, reduced maintenance costs, longer engine life, EPA registration, does not void manufacturer warranties.

The EPA emissions standards relate to four major components in the exhaust stream.


  • Particulate matter (PM), a complex set of hydrocarbon and soot material that in older engines is visible as soot in the exhaust. (Today’s cleaner engines do not emit visible smoke; the PM level is so low that it can only be observed and measured by very sensitive equipment).
  • Hydrocarbons, both pure methane (HC) and non-methane (NMHC) varieties. Hydrocarbons are sensible by their distinctive odor.
  • Oxides of nitrogen (NOx), a set of complex compounds resulting from the combustion of the intake air, which is rich in nitrogen. NOx is not sensible, but when combined with hydrocarbons in sunlight, it produces smog and ozone.
  • Carbon monoxide (CO), produced by incomplete combustion. This compound has no odor and is not visible but is that sneaky thing that your mother warned can kill you in a closed car or garage and is hazardous to people with respiratory problems when present in the atmosphere.


    What they promise
    Aftermarket suppliers will promise to reduce some or all of these factors with a variety of test methods described or implied and reductions expressed in various quantitative units and/or percentage values. In the second part of this article, we’ll investigate the industry standard method of measurement.

    Increased fuel economy. Aftermarket suppliers will claim that the product will reduce fuel consumption by some method of improving the combustion process, cleaning the combustion chamber and/or reducing engine friction. Verification of the claims is presented in the form of customer testimonials based on fleet experience and sometimes on some form of chassis dynamometer evaluation. Remember that the EPA has no fuel economy standards for heavy-duty vehicles such as school buses.

    Reduced maintenance costs. These claims focus on factors such as extended oil drain intervals, filters with longer change intervals or improved filtration capability and reduced engine wear.

    Maintenance cost in general and oil drain intervals in particular are competitive cost factors in marketing engines. If a manufacturer can develop means of reducing maintenance costs, it can be marketed and sold as a competitive advantage, so the manufacturers expend considerable time and money in minimizing their cost of maintenance through improved oil formulations, better filtration, etc. The hazards of user extension of oil drain intervals are discussed in Part 2 of this article.

    Longer engine life. There is a lot of commonality between this and the maintenance situation. The longer life is usually associated with better lube oil filtration, “cleaner-burning” additives to make the engine cleaner, reducing friction, etc. There is no quick test to verify the veracity of these claims. Engine manufacturers rely on dynamometer testing as the primary measure of engine life, and these evaluations require thousands of hours of running time.

    EPA registration. Sounds like EPA approval, doesn’t it? Well, it’s not. “Registered” implies approval without actually saying it. This claim is usually associated with additives, because every gasoline or diesel fuel additive must be registered with the EPA before it can be sold. The registration process (fill out a form) asks for a chemical description of the product but does not require an analysis of the impact of the product on engine exhaust emissions performance. You can look it up. Go to and insert the name of your candidate additive in the search engine and it will lead you to the 250-page list of registered fuel additives. I asked the EPA for a copy of a particular registration document but was refused because these submissions are confidential(!).

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