Fuel dyes

Fuel dyes are dyes added to fuels, as in some countries it is required by law to dye a low-tax fuel to deter its use in applications intended for higher-taxed ones. Untaxed fuels are referred to as "dyed", while taxed ones are called "clear".

The dyes used have to be soluble in hydrocarbon-based nonpolar solvents ("solvent dyes"), and therefore in the fuels they are added to. Red dyes are often various diazo dyes, eg. Solvent Red 19, Solvent Red 24, and Solvent Red 26. Anthraquinone dyes are used for green and blue shades, eg. Solvent Green 33, Solvent Blue 35 and Solvent Blue 26.

Due to technological requirements, it is advantageous to mix a liquid with a liquid instead of handling powdered dyes. The pure dyes are solid crystalline materials, therefore they have to be highly soluble, so concentrated solutions can be used instead.

Aviation gasoline is dyed, both for tax reasons (avgas is typically taxed to support aviation infrastructure) as well as safety -- there being obvious and disastrous consequences of fueling an aircraft with the wrong kind of fuel.

Fuel Dye in the European Union

After August 2002, all European Union countries became obliged to add about 6 mg/l of Solvent Yellow 124, a dye with structure similar to Solvent Yellow 56. This dye can be easily hydrolyzed with acids, splitting off the acetal group responsible for its solubility in nonpolar solvents, and yielding a water-soluble form. Like a similar methyl orange dye, it changes color to red in acidic pH. It can be easily detected in the fuel at levels as low as 0.3 ppm by extraction to a diluted hydrochloric acid, allowing detection of the red diesel added into motor diesel in amounts as low as 2-3%.

Fuel Dye in the United States

In United States of America, the Environmental Protection Agency mandates use of a red dye to identify high-sulfur fuels for off-road use. Solvent Red 26 is used in the United States as a standard, though it is often replaced with Solvent Red 164, similar to Solvent Red 26 but with longer alkyl chains. The Internal Revenue Service mandates use of the same red dyes, in fivefold concentration, for tax-exempt diesel fuels; their argument for the higher dye content is to allow detection even when diluted with "legal" fuel. Detection of red-dyed fuel in the fuel system of an on-road vehicle will incur substantial penalties.

Fuel Dye in the United Kingdom

In the United Kingdom, "red diesel" is dyed gas oil for registered agricultural or construction vehicles such as tractors, excavators, cranes and some other non-road applications such as boats. Red diesel carries a significantly reduced tax levy than un-dyed diesel fuel used in ordinary road vehicles. As red diesel is widely available in the UK, the authorities regularly carry out roadside checks and unauthorized use incurs heavy fines. Despite this, spot checks have occasionally found as many as one in five motorists using red diesel.

Fuel laundering - processing fuel to remove the dye so it may be illicitly sold to motorists - is a recognized criminal activity in the United Kingdom. In Northern Ireland, it has been a means of fund raising by illegal paramilitary organizations. In 2004, Northern Irish police discovered an illegal facility capable of processing 12 million litres of fuel per year.

Dyes Used

Some dyes required in some countries are listed here:

Country	Fuel	Dye
Australia	Regular Unleaded Petrol	Purple (or bronze)
Australia	Premium Unleaded Petrol	Yellow
Austria	Heating oil	any red dye
Canada	Agricultural Fuel	red/purple dye
France	Gas oil	Solvent Red 24
France	Marine diesel	Solvent Blue 35
Estonia	Heating oil	Automate Red NR or similar + Solvent Yellow 124
Estonia	Agricultural diesel	Automate Blue 8 GHF or similar + Solvent Yellow 124
Germany	Heating oil	Solvent Red 19 and similar
Greece	Heating oil	any red dye
Greece	Marine diesel	any black dye
Ireland	Gas oil	Solvent Blue 79
Ireland	Kerosene	Solvent Red 19 and similar
Italy	Heating oil	Solvent Red 161
Italy	Gas oil	Solvent Green 33
Netherlands	Agricultural diesel	any red dye and the additive Furfural
Norway	Agricultural diesel	any green dye
Portugal	Agricultural diesel	Solvent Blue 35
Portugal	Heating oil	Solvent Red 19 and similar
Spain	Agricultural diesel	any red dye
Spain	Heating oil	any blue dye
Sweden	Heating oil	Solvent Blue 35, Solvent Blue 79, Solvent Blue 98
United Kingdom	Gas oil ("Red Diesel")	Solvent Red 24, quinizarin
United Kingdom	Rebated kerosene	Coumarin
European Union	many rebated	Solvent Yellow 124 ("Euromarker")
USA	low-tax fuels, high-sulfur fuels	Solvent Red 26, Solvent Red 164
Worldwide	Aviation gasoline 80/87	red dye
Worldwide	Aviation gasoline 82UL	purple dye
Worldwide	Aviation gasoline 100LL	blue dye
Worldwide	Aviation gasoline 100/130	green dye

References

External links

• Minnesota State Patrol Commercial Vehicle Enforcement Dyed Fuel Program
• Shell information on aviation gasoline specifications