Fuel dye

"Purple gas" redirects here. For the film, see Purple Gas.

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" or "white".

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

The pure dyes found in modern liquid petroleum dyes are essentially longer alkyl side chain forms of traditional dyes and normally multiple chain length variations of the chromophore are found within a typical commercial liquid petroleum dye. For instance, Sudan Red 462 is essentially Solvent Red 19, with the ethyl side chain replaced by either a 2-ethylhexyl or a tridecyl side chain. The longer branched side chains improve solubility dramatically, but in some cases the high solubility prevents the dye being isolated as a crystal, except at very low temperatures. The high solubility liquid dyes originated with Morton International and BASF (ACNA Italy) as the primary inventors. For instance, Morton International created Solvent Blue 98 as a high solubility form of Solvent Blue 35. BASF created Solvent Blue 79 as its high solubility form of Solvent Blue 35. In some cases it is possible, with normal solvents—e.g., xylene—to prepare stable (to -20C) solutions at 65% "solids" content. The original powder dye form of the chromophore would not be soluble beyond 2% in xylene.

Only a few refineries worldwide still use powder dyes for colouring fuels, as ultimately they are still lower cost per active molecule of dye chromophore than the modified forms. They have significant handling issues and health and safety issues that inherently arise from the handling of azo dyes (reds/yellows/green mixes). It is advantageous to mix a liquid with a liquid instead of handling powdered dyes into a liquid.

Aviation gasoline is dyed, both for tax reasons (avgas is typically taxed to support aviation infrastructure) as well as safety (due to the 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, to heating fuel. 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%. The European Union has announced that has found a new and better marker to replace Solvent Yellow 124.

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 compared to 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. Unauthorized use incurs heavy fines but despite this spot checks have occasionally found as many as one in five motorists using red diesel.

Red diesel can also be used in road vehicles which are registered as off-road with the DVLA provided they are only used on private land. On 14 July 2014, the European Commission announced it was referring the United Kingdom to the European Court of Justice over the use of red-diesel in propelling private pleasure craft on water. It believes the UK is not properly applying EU regulations for the fiscal marking of fuels.

On 18 November 2014, a new measure to combat fuel laundering should result in the illegal trade being "virtually eliminated" in the United Kingdom, according to HM Revenue and Customs. A new dye will be introduced in April 2015 in the United Kingdom and the Republic of Ireland.

Carbon Offset Red Diesel

Carbon Offset Red Diesel is now available in the UK. It is an environmentally friendly alternative to regular red diesel. There is an extra cost incurred when purchasing Carbon Offset Red Diesel, however some suppliers of the fuel are donating the extra cost to projects aimed at lowering carbon emissions, meaning they make no extra profit from the sale of Carbon Offset Red Diesel.

Poland

Currently there are no naked-eye visible dyes in car fuels sold in Poland. However, during the time of Communist Party rule, the state-owned CPN fuel monopoly dyed leaded gasolines (marketed as "ethilins") in the following colors: 78 – blue, 86 – green, 94 – yellow, 98 – red. Diesel fuel, although unleaded, was also dyed a brown color.

Fuel dye in North America

In the 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, which is similar to Solvent Red 26 but with longer alkyl chains. The Internal Revenue Service regulation 26 CFR 48.4082-1 mandates use of the same red dyes, in fivefold concentration, for tax-exempt diesel fuels such as heating oil; 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 laundering

Organised crime gangs may "launder" low-price dyed fuel, removing the dye and selling it illegally to unsuspecting motorists at the higher price of undyed fuel. Paramilitary groups connected to political unrest in Northern Ireland have established laundering plants on both sides of the Irish border. In 2004, Northern Irish police discovered an illegal facility capable of removing the dye from 12 million litres of fuel per year. In 2009, customs officials shut down a plant capable of removing the dye from 6.5 million litres of fuel per year. In 2011, a plant capable of processing 30 million litres was discovered.

Fuel theft

Fuel is being dyed by companies such as Bord na Móna in Ireland in an effort to combat the widespread theft of fuel.

Dyes used

Some dyes required in some countries are listed here:

Country	Fuel	Dye
Australia	Regular unleaded petrol	purple/bronze (changed to red/orange in 2013)
	Premium unleaded petrol	yellow
Austria	Heating oil	any red dye and Solvent Yellow 124
Canada	Off-road fuel (agriculture, construction, mining etc.)	red/purple dye
	Marine gasoline	any red dye
	Heating oil	any red dye
Finland	Heating oil	Solvent Yellow 124
	Diesel for construction and agriculture	Solvent Yellow 124
France	Diesel (heating/off-road)	Solvent Red 24 and Solvent Yellow 124
	Marine diesel	Solvent Blue 35
Latvia	Heating oil	The used chemical substance is N-ethyl-N- [2- (1-iso butoxyethoxy) ethyl] azobenzene-4-amine (Solvent Yellow 124). SIA “Straujupīte” for diesel labeling is using no more than 0.2% of sulfur content. Diesel is labeled by adding one of the coloring matters to 1000 liters of oil products:: (N-ethyl-1- (4-fenilazofenilazo) naphthyl-2-amine – at least 5.0 grams;
	Agricultural diesel	fiscal marker - chemical N-ethyl-N- [2- (1-isobutoxyethoxy) ethyl] -4- (phenylazo) aniline (Solvent Yellow 124, CAS Nr.34432-92-3) - at least 6.0 grams, and no more than 9.0 grams; on 1000l
		blue colorant 1,4-bis (butylamino) -9,10-anthraquinone (Sovlent Blue 35, CAS no. 17354-14-2) or any other equivalent blue coloring - at least 7.0 grams on 1000l
Estonia	Heating oil	Automate Red NR or similar
	Agricultural diesel	Automate Blue 8 GHF or similar
Germany	Heating oil	Solvent Yellow 124 + 4.1 gr/litre Solvent Red 19 or 5.3 gr tolyazotolyazo-ethylhexylbetanaphthylamine or 6.1 gr tolyazotolyazo-tridecylbetanaphthylamine & similar
Greece	Heating oil	any red dye
	Marine diesel	any black dye
Hungary	Heating oil	Ferrocene
Indonesia	Pertalite (RON 90)	Green dye
	PERTAMAX (RON 92)	Blue dye
	PERTAMAX Turbo (RON 98)	Red dye
Ireland	Gas oil	green dye = Solvent Yellow 124 and Anthraquinone Blue dye equivalent to Solvent Blue 35 and ACCUTRACE S10 ((3-(sec-butyl)-4-(decyloxy)phenyl)methanetriyl)tribenzene]]
	Kerosene	Solvent Red 19, Solvent Yellow 124 and ACCUTRACE S10 ((3-(sec-butyl)-4-(decyloxy)phenyl)methanetriyl)tribenzene
Italy	Heating oil	Solvent Red 161
	Gas oil	Solvent Green 32 or 33 and Solvent Yellow 124
Netherlands	Agricultural diesel	any red dye and Solvent Yellow 124 (the additive Furfural is obsolete)
Norway	Agricultural diesel	any green dye
Portugal	Agricultural diesel	Solvent Blue 35
	Heating oil	Solvent Red 19 and similar
Spain	Agricultural diesel	any red dye + Solvent Yellow 124: Orden PRE/1724/2002 of the 5th of July.
	Heating oil	any blue dye + Solvent Yellow 124: Orden PRE/1724/2002 of the 5th of July.
Sweden	Heating oil	Solvent Blue 35, Solvent Blue 79, Solvent Blue 98 and Solvent Yellow 124
Thailand	Gasoline 95	yellow dye
	Gasoline 91	red dye
United Kingdom	Gas oil ("red diesel")	Solvent Red 24, quinizarin, Solvent Yellow 124 and ((3-(sec-butyl)-4-(decyloxy)phenyl)methanetriyl)tribenzene
	Rebated kerosene	Coumarin, Solvent Yellow 124 and ((3-(sec-butyl)-4-(decyloxy)phenyl)methanetriyl)tribenzene
Europe	many rebated	Solvent Yellow 124 ("Euromarker")
United States	low-tax fuels, high-sulfur fuels	Solvent Red 26 3.9lbs per 1000 barrels, Solvent Red 164
Worldwide	Aviation gasoline 80/87	red dye
	Aviation gasoline 82UL	purple dye
	Aviation gasoline 100LL	blue dye
	Aviation gasoline 100/130	green dye

External links

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