What changes do you need to make to your fuel store to avoid problems with the new ultra-low sulphur gas oil that replaced good old red diesel?

If it’s a reasonably new plastic bunded fuel station with a filter and a tap to let off the water then you’re probably fine. But if it’s a steel tank that was installed in 1972, it may be time to give it a bit of attention. The reason is simple. Until recently, tractor engines were pretty tolerant of crud and water, so fuel filters had relatively coarse elements in them. But the arrival of common-rail diesel engines (which pressurise the fuel to high levels and squirt it through sophisticated, solenoid-operated injectors) meant dirty fuel was no longer up to the job.

To protect their engines, tractor makers are fitting ever finer fuel filters (down to as little as 3 microns), which do their job well but soon block up if you continue to put grubby diesel through them.

At the same time, the new fuel has up to 7% biodiesel in it. Great news on the renewable energy front, but biodiesel has some less desirable qualities. One is that it extracts moisture from the air with all the enthusiasm of a bank chief executive grabbing his end-of-year bonus.

The other is that biodiesel doesn’t have the keeping quality of mineral diesel. Mineral red diesel is the petrochemical version of Christmas cake – happily sitting at the back of the cupboard for months without apparent decay.

However, biodiesel (even though it’s mixed in with lots of mineral diesel) has a limited shelf life. Once it starts to decay (which can be anything from six months to a year, depending on who you talk to), it provides a great food for algae and other microbial nasties and can block a tractor fuel filter in no time.

There’s a third problem, too, and that’s biodiesel’s scouring effect on old tanks, This means that much of the crud that happily adhered to the tank walls year after year may now get sucked back into the fuel.

This is early days for the new diesel, and even the experts are unsure about how much or little of a problem it will all cause. But one area they reckon farmers should tackle immediately is the filtration and water let-off facilities on the farm’s fuel store itself.

One person who knows as much about filters as anyone is the boss of Derbyshire filter specialist AB Components, James Edgar. He points out that one of the problems is the lack of fuel filters on the market which tell you when they are full.

He has now sourced three different units, all designed to fit farm fuel stores, that give good filtration and warn you when it’s time to change the elements.

* The Series II unit is suitable for gravity-fed or pumped systems. It has a flow-rate of 110 litres/minute and filters out particulates down to 10 microns (30 microns for gravity-fed systems), as well as absorbing free water from the fuel.

An indicator shows if there’s a flow restriction, meaning the filter is becoming blocked by water or particulates. Cost is £149 (including a spare element) for a pump-fed system and £189 for a gravity-fed version. Elements cost £25 for the pump-fed unit and £37 for the gravity-fed version.

* The Series III unit is essentially a double version of the Series II, so intervals are longer between element changes. It is for pump-fed systems only and has the same indicator that shows when the filters are getting blocked. Price is £330, including a pair of spare elements, and new elements cost £50 for a pair.

* The Series IV costs £1159 so is aimed at big farms and contractors. It’s a smaller version of the same Separ filter used in heavy-duty applications such as military vehicles and lifeboats. As well as filtering down to 10 microns, it allows the farmer to drain off the free water and some of the emulsified water (which is often the stuff that freezes in pipes first) as well. Elements cost £75 but Mr Edgar says they last longer than the Series II and III equivalents.

One downside is a lower 40 litres/minute flowrate – two minutes to fill a typical 80-ltre tractor tank.

* AB Components now also sells a Stanadyne Fuel Manager fuel/water separator for tractors with pre-common-rail engines, which has a yellow indicator that pops out when the filter is blocked. It also now stocks £100 air-vent breathers that use water-absorbing crystals to stop moisture getting into the fuel tank that way.