In order to meet emissions targets, from the start of 2011, red diesel sold for use in tractors and other farm vehicles now has a lower sulphur content and may contain up to 7% biofuel. 
To get the best from your machinery, it is important to have an understanding of the type of red diesel you may be supplied with and how it should be stored to keep it at its best.
The basics
Fuel sold to power mobile equipment on farms should meet one of two quality standards:
- BS2869:2010 (Part 1 Class A2), commonly known as gas oil; or
- EN590: 2009 which is essentially the same specification as white diesel.
When sold for agricultural use, both of these fuels are supplied with a red excise dye marker and will have a low sulphur content.
However, there are three main differences to be aware of:
- Diesel has a slightly lower waxing point and should survive to temperatures of at least -15°C in the winter, with gas oil good to at least -12°C.
- Diesel has a higher cetane number than gas oil, which means that it should burn better and will almost certainly be more suited to modern engines.
- Diesel has a much higher chance of containing biofuel than gas oil, which will mean that you will need to take extra care when storing this fuel.
It is important to note that these values are minimum standards and that if your fuel is good quality you would expect it to exceed the thresholds for cetane and waxing (cold filter plugging) point.
Biofuel
You should check with your fuel company to see what red diesel you are being supplied with, if it is likely to have biofuel in it and at what level.
The major oil companies currently estimate that BS2869:2010 A2 gas oil should not typically have more than 2% biofuel and that at these levels there should not be a problem with storage. It is not economic to put biofuel in gas oil past these levels as it is priced at a premium and there is no legal minimum inclusion level for off road vehicles. The reason that gas oil may have some biofuel in is due to residue in the lines from refinery to terminal and from the occasional batch of downgraded EN590 into the gas oil supply chain.
This is not a new situation and it is quite probable that your gas oil supply has had a low level of biofuel in some for time, however the reduction in sulphur level has reduced the overall stability of the fuel and so more care is needed at storage.
Best advice on fuel storage and use is to:
- Replace fuel filters after the first two to three tanks of the new fuel as the biofuel can pick up debris in tanks and flush it into the filters. For this reason, it’s also a good idea to use filters on storage tanks to catch most of the debris before it gets into the tractor tank.
- Keep water out of your storage tanks, as biofuel can absorb water into the fuel and this may lead to bacterial growth and sludge forming in the fuel. As well as keeping rain water out of tanks, there are water eliminator products to help absorb any water in fuel.
- Don’t store fuel with biofuel in for much more than 6 months and certainly no more than 12 months to help prevent this sludge forming which can block filters.
These guidelines are particularly important if your fuel is more likely to contain biofuel at levels above 2%, for instance if you have ordered or have been told you are being supplied with EN590.
Cetane number
The cetane number (CN) of a fuel is a measure of the ignition delay. Fuels with a higher CN have shorter ignition delays and provide more time for the fuel combustion process to be completed. Hence, higher speed diesels operate more effectively with higher CN fuels.
EN590 has a minimum CN of 51, while BS2869:2010 has a minimum CN of 45.
Generally, diesel engines run well with a CN from 40 to 55. Many manufacturers recommend using an EN590 specification fuel as that is what modern engines have been designed to run best on.
If you are being supplied with gas oil and are concerned about the cetane number, there are various additives available which aim to bridge the gap as well as helping the fuel burn cleaner to reduce engine deposits in delicate parts such as the injectors. Cetane numbers shouldn’t be an issue in older tractors as combustion standards of BS2869:2010 should match what the engines were designed to run at.
Stationary equipment
There is no requirement for gas oil used in heating and fixed equipment to be low in sulphur. This could include machinery such as fixed grain driers and generators, feed mills and also domestic equipment such as heating systems and even some Agas. However, some fuel suppliers may decide to sell you sulphur free fuel for these applications as well, in which case the precautions discussed in this article for equipment and storage will be equally applicable.
Check with your machinery manufacturer that the quality of fuel is appropriate for your equipment and make sure you know what you're ordering from the supplier. The specification to look for is BS2869:2010 Part 2 Class D high sulphur. Be aware though that not all suppliers will stock this fuel type and it is not guaranteed to be free from biofuel.
- John Hall - 29/12/2011
Yet again we have been sold down the river.
When this "new fuel" was announced we were told by those above that it would contain a higher % of bio and it should not be mixed with the old type gas oil or we would get problems with engines.
Now we don't know what the hell we are buying!
and yet again we have to sort out the problems of what we are being supplied with. Will someone in the NFU get on & sort this mess out regarding different types of fuel before we all go bust from paying for new engines/fuel systems ect. We should have told europe to get lost about emisson targets all the marine people did. We the daft farmers just bowed down to authority yet again.
Our fuel supplier doesnt know what we are being supplied with and it appears from this write up that the major oil companies dont either.
In over 65 tears of farming with diesel engines we have never had any major problems with fuel but the last 2 years have been an expensive nightmare for us and many more end users of the expensive rubbish being passed on to us as so called fuel.