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FUELSTAT® On-site Test Kits - Diesel 

The On-site FUELSTAT® Diesel test kit box includes 8 individual tests.


  • FUELSTAT® DIESEL is an IATA approved, on site diesel bug test.
  • In just 10 minutes, without any special skills or equipment, the pregnancy style fuel testing technology allows quick and easy detection of fuel contamination.
  • Detect both high and low levels of fuel contamination within minutes.
  • Accurately identify the type of contaminants that may be present in your fuel.
  • Discover fuel contamination at an early stage before it becomes problematic.
  • Easily determine the right course of action to treat the problem.
  • Keep a simple log of test results using the easy to read test paddles.
  • All components of the FUELSTAT® DIESEL on site fuel test are completely disposable.


  • There are a number of different types of microorganisms that can grow in certain types of fuel.
  • The biggest problem is presented by a filamentous fungus called Hormoconis resinae, (H Res).  
  • Previously called Cladosporium resinae, and more commonly referred to as “the diesel bug”.
  • H Res is a fungus that thrives in diesel fuel. It requires only a minimal amount of water content in the fuel to grow and will cause filter blockages, component failure and tank corrosion if left unchecked. Bacteria and other types of fungi, particularly some yeasts can also cause problems in fuel tanks, usually acting as a consortium.
  • The objective of this test is to provide rapid screening of fuel samples (water in fuel or fuel), giving a quick and accurate assessment of H Res, bacteria & other fungi including yeasts in the fuel tank.
  • This test is unlike current growth-based tests which require a minimum of 72 hours to provide any results.
  • The test measures the amount of active growth in the sample and provides actions and alert levels.
  • The FUELSTAT® resinae PLUS DIESEL test measures the amount of different types of contamination: H Res, bacteria and fungi actively growing in the sample and reports that as the weight of material in the sample. This is a newer, more accurate measurement system than the old Colony Forming Unit (CFU) count.
  • The test provides results based on a traffic light scenario:
  1.  Negligible (green) – negligible contamination
  2.  Low Positive (amber) – moderate contamination
  3.  High Positive (red) – heavy contamination
  • 6 Devices are included in every Test Kit

Right side of paddle (LOW) 3 devices with cut off levels for H Res, bacteria and fungi at a level derived from IATA Guidance Material where the microbes have established themselves as a consortium and a fuel treatment is required.

Left side of paddle (HIGH) 3 devices with cut off levels for H Res, bacteria and fungi at a level derived from IATA Guidance Material where the microbes are growing so rapidly, or have been growing for a long time that they may be causing damage to the structure of the tank or are likely to cause filter blockage and component failure and a tank clean and fuel treatment are required.

Test Kit Contents

  • Each heat sealed foil pouch contains a Paddle with desiccant sachet and pipette in one section and Sample Extraction Bottle with flat cap, dropper cap and instructions for use in the other section.
  • Paddle: Plastic base with 6 lateral flow devices affixed.
  • Preparation Bottles: 175ml plastic bottle with flat cap and “dropper” cap containing 3.0ml of Sample  Extraction Liquid.
  • Disposable, single use, plastic pipette.
  • Instruction leaflet.

Fuel Husbandry

  • Rather than treat contamination when significant operational or fuel quality problems arise it is better to prevent microbial growth occurring. Much can be done to ameliorate problems associated with microbial contamination in fuels, these include;
  •  Allowing fuel deliveries to settle in the tank for 24 hours before putting the tank back into service.
  •  Drain any accumulated water from the bottom of the tank weekly.
  •  Routinely test bottom samples for microbial contamination.
  •  Treat fuel if required, according to test results.


  • The FUELSTAT® resinae PLUS DIESEL test utilises lateral flow technology and antibodies to H Res, bacteria and fungi which grow in diesel fuel.
  • The gold-labelled antibody is immobilised in the Release Pad under the sample well.
  • The sample containing an unknown amount of contamination is added to the sample well and this re-hydrates, allowing the reagents to flow up (wicking) the membrane towards the absorbent pad.
  • Any large particles in the sample, which may block the reaction, are blocked by the filtering action of the pad.
  • During the wicking, the contamination in the sample will bind to the specific antibodies.
  • As the liquid reaches the Test Line (T) any free gold-labelled antibodies will bind to the test line.
  • This means if more contamination is in the sample than the threshold engineered, there will be no antibodies to bind to the Test Line, no red line will appear, and this is a POSITIVE result.
  • If the amount of contamination in the sample is lower than the threshold, there will be free antibodies to bind to the Test Line, a red line will appear, and this is a NEGLIGIBLE result.
  • The quantities of materials immobilised in the device are engineered to provide results at the different thresholds of H Res, bacteria and fungi in each of the test devices on the Test Paddle.

Sample Preparation

  • Take a sample from the fuel tank into a clean container.
  • Allow the sample to “settle” and any water to accumulate at the bottom of the sampling container.
  • Ideally, the sample should be drawn from the tank sump or lowest point from a water drain point.
  • Alternatively, draw a tank bottom sample using a dipped sample tube from the tank fill aperture.
  • For vehicle tank testing, if it is impossible to harvest a tank bottom sample then the contents of the primary fuel filter is the next best place.
  • This sample however may not represent the tank bottom.
  • Any sample taken should be tested as soon as possible after collecting and, in any event within 6 hours to maintain the integrity of the sample.

NOTE : When possible, test the water phase of the sample taken from the fuel tank. Testing the water phase will provide more accurate results than testing the fuel phase.

What is the Diesel Bug?

  • The Diesel Bug is a consortium of organisms which live at the fuel water interface.
  • They live in the water phase whilst feeding on the fuel.  
  • Of all the organisms in this consortium, H res is the most recognisable and also damaging component of ‘sludge’. 
  • This fungus is the main culprit in instances of filter blockage & tank corrosion when left unchecked.
  • The rest of the consortium includes bacteria and other types of fungi, particularly some yeasts which can also cause fuel system problems.

How has Fuel Changed?

  • The combined effects of adding FAME (Fatty Acid Methyl Esters) and reducing sulphur have changed the characteristics of diesel fuel.
  • The fuel supply chain is adapting to deal with the consequences in storage, from distribution to storage and right through to vehicles.
  • Avoiding water is much more difficult now as FAME, being hygroscopic, attracts it. 
  • With more water comes increased incidence of injector problems, corrosion and lubricity issues.
  • Then there is, of course, microbial contamination aka ‘diesel bug’.

Why Test?

  • Fuel testing puts you in control.
  • It establishes the status of your fuel and tank.
  • As an alternative to guesswork or additives, fuel testing allows you to diagnose and appropriately treat operating diesel fuel system problems in both vehicles and tanks.
  • By designing a regular monitoring regime you catch problems early before they result in costly operational issues.
Contact PETRO industrial's team of bulk fuel storage and dispensing specialists for more information today!