119.0   Additives and secondary additives for fuels

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Additives and secondary additives for fuels

Due to the increased demands placed on fuels, it is necessary to optimize certain properties of the base fuels. Additives can lend additional properties to fuels or increase or mitigate existing properties. Additives are fuel-soluble compounds of mainly organic chemical nature.

A variety of properties can be influenced by additives, they e.g. prevent or reduce the formation of deposits of combustion products in the fuel injection system and engine or corrosion damage in the fuel system. Usage properties can also be improved using additives, a foam-inhibiting additive is e.g. frequently used in diesel fuels.

Numerous additives are used in commercially available fuels. Some examples are listed below.

Gasoline
  • Octane number booster
  • Detergents
  • Corrosion inhibitors
  • Antioxidants
  • Conductivity booster
  • Dyes/markers
  • Demulsifying agent
Diesel fuel
  • Cetane number booster
  • Detergents
  • Corrosion inhibitors
  • Antioxidants
  • Conductivity booster
  • Foam-inhibiting additives
  • Flowability booster
  • Lubricity booster
  • Dyes/markers
  • Demulsifying agent


A special case are organometallic compounds such as e g. methylcyclopentadienyl manganese tricarbonyl, ferrocene and tetraethyl lead which are still used in some countries to boost the octane number. These additives have very negative effects on the advanced engine and exhaust treatment technology. The Worldwide Fuel Charter therefore advises against the use of additives forming ashes (containing metal).

Extensive research has shown that the use of gasoline and diesel fuels with high additivity levels is a necessary measure, and in the long term also a cost-effective one, for the service life and cleanliness of engines and fuel systems, maintenance of favorable exhaust emission values as well as for achieving a good performance overall.

In terms of the supply of such fuels, the individual customer must rely on the filling stations that he/she visits selling such fuels with additives; the opinion of large companies passed-on to us has shown that this is the case nationally, and is usually the case in respect of independent filling stations not tied to major suppliers. Fleet owners should therefore ensure that products with additives are delivered when negotiating on a bi-lateral level.

The correct selection, application and metering of such additives depend on detailed research in the laboratory, on test benches and in vehicles, so that the effect of the additives is optimized for the respective fuel, additives are adapted to each other and do not cause any negative side effects. Since the consumer will generally not have the required facilities for this, mixing additives to fuels may be the exclusive preserve of the manufacturers of such fuels.

However, drivers are constantly being offered fuel additives with the promise of huge success, such as higher engine output at lower fuel consumption, for example. For better distinction, we have designated these additives secondary additives . Our vehicle engines generally do not require such secondary additives, since in most cases uniform and adequate grades of fuel can be assumed. Special attention should be paid to making sure that only the fuel grade recommended by us is used. The use of secondary additives however, is mostly an additional cost burden that is not necessary and in the worst case it can lead to permanent damage. In individual markets with a poor fuel grade, additional use of additives may be required. In such special instance, additives which are tried and tested and approved for Mercedes-Benz vehicles are recommended by the Mercedes-Benz specialist workshops. Please ensure that you observe the instructions and mixing ratios specified on the container.

We strongly advise against the use of secondary additives that are not approved by Mercedes-Benz. The application of secondary additives is always at the risk of the operator of the vehicle, since their use may impair any warranty issued both by the manufacturer of the vehicle and the fuel supplier.