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Testing Diesel fuel in 2021

Diesel fuel

Diesel fuel is important, and testing your diesel fuel is crucial. Generator fuel can be equally as valuable as the generator itself. You can conduct cursory testing by doing sensory checks (Does it look ok? Is there any sediment, dirt, or anything visible?), but further knowledge of the fuel’s condition is requires more substantive testing.

Companies that store fuel need to know whether fuel still meets specifications and will still work properly when needed. In other words, they use diesel fuel testing to determine the combustion quality and stability of the fuel.  Our testing program adheres to the requirements of NFPA 110


Diesel fuels can be contaminated through the introduction of water, other fuels, microbes, and particulates like rust, dirt or sediment.

Within your fuel tank, the thermal expansion occurring when fuel heats and cools can cause condensation to form. Condensation adds water to fuel, which provides a medium for algae to grow. Algae feeds on the water and can grow exponentially. Diesel fuel additives may be used should water contaminate a full system.

Biodiesel fuel is composed of FAME (fatty acid methyl esters) which retain more water than refined diesel fuel.

Generators located in tropical areas may also be more susceptible to becoming tainted due to higher humidity in these regions. The moisture in the air and variations in temperature create the ideal environment for condensation and contamination to occur. When fuel isnt filtered often, it can build up to dangerous levels.

Using contaminated fuel must be avoided because of the numerous problems that may occur. Water coming in contact with injection pumps and injectors can irreparably damage the fuel injection system. If that happens, internal parts would need to be disassembled and repaired or replaced. This could cost up to tens of thousands of dollars, depending on the scope and size of the generator.

Water in fuel tanks can also threaten the function of the engine. Performing generator diesel testing annually can ensure that the fuel is continually suitable for use or not.


Regular fuel maintenance programs that detect levels of water measure the overall quality are the best way to prevent any issues with your diesel fuel. One way to maintain low levels of contamination is to consistently remove water from fuel tanks, as this can prevent the growth of yeast and bacteria.

Of course, generator diesel testing is an essential part of any fuel maintenance regimen. Testing allows you to identify microbial contamination and other problems at its earlier stages, allowing you to take early action. This will protect your generator performance and save you money in the long run.

If contamination is dangerously high, specialist fuel cleansers and biocides can be used. This is a costly process, as advanced treatment of contaminated fuel and generators can cost many thousands of dollars while taking your equipment out of commission.

The best way to prevent microbial contamination is to ensure there is no moisture within the fuel as well as dry the fuel by circulating across specialized filtration.


Oxidative Stability

Testing for oxidative stability in fuel from diesel engines provides insight to longterm storage stability. Oxidative stability testing is a predictive test that measures sludge formation and varnish development when fuel is exposed to accelerated stability conditions. 

Poor ox stab values indicate the fuel may not be suitable to use after storing in a tank for longer periods of time.

Sediment and Water Levels

Especially in critical facilities, including many healthcare locations, testing for sediment and water content in diesel fuel is required. High levels of water or sediment prevent equipment from working properly, which can have massive ramifications. 

Sulfur Content

Regulations now require many diesel fuels to have sulfur content below 15 ppm, making this test essential for liability purposes. Generator diesel testing can prevent any issues if fuel is spot-checked for sulfur. EPA on site audits may perform immediate sulfur analysis to ensure compliance, and fines for out-of-tolerance sulfur amounts are substantial.

Cetane Rating

Similar to gasoline’s octane rating, cetane rating measures diesel fuel combustion quality. Cetane rating can decline over time as fuel is stored. The presence of negative environmental conditions, water sediment, large temperature changes and microbes, can hasten this decline.

Fuels with insufficient cetane rating will not lead to efficient function of engine startup and operation. Even if the engine is able to run, it will not run smoothly. The look and smell of fuel will not be adequate to determine its cetane rating, so lab testing is the only way to know for certain.


It may be necessary to “polish” the fuel should the lab analysis finds out-of-tolerance fuel specification. Regular and spot filtration may provide immediate improvement.


At Peak Petroleum Testing Services, weve provided comprehensive and high-quality testing for our customers since our start in 2001. We follow all specifications from the United States Environmental Protection Agency and can make recommendations for your diesel fuel depending on your needs.

Having a trusted provider test your diesel fuel will give you the confidence that your equipment has the fuel it needs to work properly. American Society of Testing and Materials (ASTM) list the methodology to prove compliance towards specifications developed by the producers, consumer, and testing labs around the world.

Contact us to speak with an expert about your diesel fuel!

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Petroleum Testing Services

petroleum testing


Petroleum testing is performed on petroleum components and byproducts: crude oil, shale oil, natural gas, fuel, and upstream oil and gas. Petroleum testing services involve the analysis of crude oil fractions and composition as well as researching the fuel additives and oil contaminants.

Though petroleum testing is most commonly done within the petroleum industry, testing can have alternative uses. It can be done on petroleum waxes, monitoring food oils and the presence of petroleum contamination in the environment.


Because petroleum testing is done at different parts of the production process, it is necessary to understand the different steps involved. Petroleum is produced in upstream, midstream, and downstream production processes.

Upstream Process
In the petroleum industry, the upstream process involves the exploration and production of crude oil. Crude oil and natural gas fields can be searched for underground or underwater. Exploratory wells can then be drilled to bring the natural gas and crude oil to the surface.

Midstream Process
The midstream process involves transportation of crude or refined petroleum products. Transportation can be done by using trucks, oil tankers, pipelines, barges, or rails. The midstream sector also includes storage and wholesale marketing of the petroleum products The pipelines that move crude oil to refineries are also used to transport refined petroleum products to downstream distributors.

Downstream Process
The downstream process is when petroleum crude oil is refined into usable products like gasoline processed. The purified products are categorized into light distillates, middle distillates, and heavy distillates.


Petroleum can be measured for numerous properties like flash point, viscosity, volatility, oxidation stability, and cold weather stability. Different instrumentation is needed to measure different aspects of the product.

The Most Common Petroleum Testing Equipment Includes:

  • Viscometers
  • Vapor pressure analyzers
  • Flash point testers
  • Trace metals analyzers
  • Distillation equipment
  • Density meters
  • Octane number analyzers
  • Oxidation stability analyzers
  • Water content
  • Spectrophotometers
    Gas and Liquid Chromatography

Some instruments that are used to test petroleum products measure physical properties. Viscometers, flash point testers, and rheometers used in petrochemical testing measure physical properties. Other equipment is used to measure chemical properties, including mass spectrometers, elemental analyzers, sulfur analyzers, and combustion analyzers.

Depending on the setting availability and testing needs, select equipment may also be needed. For instance, specialized instruments might be necessary for in-house testing or for petroleum testing requiring rapid turnaround. Petroleum samples can also be sent out to 3rd party partners labs instead of storing and maintaining expensive in-house instruments.


Petroleum feedstock, crude oil fractions, and finished petroleum products have different requirements for petroleum testing and analysis. Hundreds of tests and protocols, including ASTM protocols, are available to use for petroleum analysis.

Gas chromatography can be used to analyze saturated fractions with conventional detectors. Gas chromatography is able to analyze hydrocarbons that have carbon numbers less than C35. Hydrocarbons that have higher carbon numbers would require specialized gas chromatography analysis.

Sensitive and selective GC detectors, can be combined with mass spectrometry. This method combines aspects of mass spectrometry with gas chromatography to identify individual components contained in a sample.

Petroleum products that are heavier-cut, including asphaltenes and resins have much higher boiling points and are analyzed using liquid chromatography-mass spectrometry.


TAN measures acidity by determining which acid compounds are present in the petrochemical products. Expressed in KOH milligrams per gram of product, the acid number measures total amount of acidic necessary to reach an endpoint detection.

TAN is measured because petroleum products can have acidic components coming from additives or as oxidation products resulting from degradation during service. The presence of acid is a risk for metal corrosion and has the potential for hindering water separation characteristics of petroleum products.


Identifying the total volume of saturates, olefins, and aromatics in petroleum fractions allows you to determine how well petroleum fractions function as feeds for catalytic reforming processes and gasoline blending elements.

The volume percent of each component is also necessary to measure fuel quality and categorize petroleum products as blending components. The concentration of aromatic hydrocarbons can influence products’ combustion characteristics, tendencies to form smoke, and how much exhaust emissions are released. This is a reason why regulations for petroleum tank testing impose limits for these characteristics.


ASTM’s Standard Methodologies provide a universally agreed upon set of values critical to Quality Control used at the refining stage and for determining the usefulness of a fuel product. They cover mechanical, physical, chemical, thermal, and rheological properties. To determine whether fuels meet the standards, they are tested for purity, density, composition, miscibility, thermal stability, toxicity, and compatibility with other materials.

Because of safety, quality, and environmental reasons, a vast number of specifications and test methods are available for petroleum products. Though this can make the many standards difficult to keep track of, their presence can still be beneficial. Having petroleum standards that are detailed and comprehensive makes it easier to determine whether fuel oils are high quality so they can be used safely, efficiently and can determine an overall suitability for use.


Petroleum tank testing is critical because many contaminants can create serious problems in product quality. The presence of contaminants also poses a risk for corroding equipment hindering catalysts required in the refining process, and forming deposits on metal parts.

Trace-level halogens and sulfur can be measured precisely by using combustion ion chromatography. Combustion ion chromatography enhances direct ion chromatography by oxidizing samples using high heat before further analysis.


Peak Petroleum Testing Services, inc is a national leader in petroleum testing and has been providing comprehensive analysis since our beginning in 2001. Our labs are precise and thorough, and we perform services backed by ISO/IEC 17025:2017 Accreditation. We’re here to help you 24/7 and provide emergency or rush testing as needed.

Contact us to speak with a petroleum testing expert!

Diesel fuel can become contaminated during long-term storage


ISO Logo

Potential issues:

  • Exposure to water.
  • Exposure to the oxygen in the air
  • Extreme heat or cold temperature swings.
  • Biological contamination (Bacteria, fungi, and mold)
  • Low quality and contaminated fuel mixed with clean fuel to solve the problem.
  • Ultra-low sulfur diesel (ULSD) has a greater tendency to oxidize than higher sulfur diesel since sulfur is a natural antioxidant.

Temperature/ Exposure to Oxygen

  • Wax crystals form when fuel is not prepared for use in cold temperatures, and those crystals will clog fuel filters.
  • Oxidized fuel is more acidic and forms larger molecules (gums, varnishes) that will fall out of solution and plug filters. Oxidation is caused by exposure to air in time. This process gets worse with more extreme temperature exposure (hot days/direct sun on tanks, and colder nights).
  • Biodiesel – Diesel blends tend to oxidize faster than Diesel alone.
  • Acidified fuel can corrode the tank which can lead to clogged filters, unnecessary generator component wear and downtime for the company.


  • Free water pooled at the bottom of diesel tanks can be drained off, but dissolved water will need to be run through water-absorbing filters.
  • Water in the fuel can lead to biological growth.

Biological growth

  • Bacteria, fungi, and mold can grow in diesel fuel and will clog filters with growth. Existing growth will need to be filtered out and treated with chemicals.

Other contaminations

  • Other tests like distillation can show if there is an appreciable amount of another fuel like gasoline or a chemical solvent.


Taking a representative sample is critical in understanding the nature of your fuel.

Different factors can determine where you sample:

  • Sampling dead bottom can give an idea of what water, sediment, and biological growth you have in the tank.
  • If you have water in the tank, sampling just above this water layer will give you an understanding of if your fuel is starting to oxidize and, also if it has biological growth.
  • However, if you suspect that your diesel has been contaminated with gasoline, for example, it would be better to sample at the top of the tank (since gasoline is less dense).
  • Taking an Upper, Middle and Lower sample might be appropriate for some tanks while taking an “All Level” sample might work for others.

The following is our recommended monitoring program:


Make Fuel Testing Part of your Maintenance Program

  • Diesel fuel testing can benefit any fuel quality assurance program by identifying problems so the fuel can be salvaged.
  • The best approach is to monitor the fuel yearly (larger group of tests) with a check-up on critical ones every three months.

Yearly Monitoring

Main sample (Sample taken above water layer (if one is present)
Cetane Index (ASTM D976) – Distillation (ASTM D86 or D7345) – Sulfur (ASTM D5453 or D7039) – Bacteria and Mold/ Fungi (D6469) – API/ Density (ASTM D4052) – Cloud Point (ASTM D5773) – Pour Point (ASTM D5949)
Sediment and Water (ASTM D2709) – Oxidation Stability (ASTM D7545) Flashpoint (ASTM D93).

Bottom sample(Sample taken at “dead bottom”)
Visual analysis (ASTM D4176)
Bacteria and Mold/ Fungi (D6469)
Sediment and Water (ASTM D2709)

Quarterly Monitoring

(Sample taken at “dead bottom”). Visual analysis (ASTM D4176) –
Sulfur (ASTM D5453 or D7039) – Sediment and Water (ASTM D2709) – Oxidation Stability (ASTM D7545) – Bacteria and Mold/ Fungi (D6469)

Other tests like Particle Count (ASTM D7619) and Karl Fischer Water Content (ASTM D6304) are available upon request.

Fuel, like the generator itself, needs maintaining, testing and continual monitoring. We can ensure that your fuel is viable and keeps your tank clean and generator running smoothly.

Be proactive with your fuel.

How to Get the Best Jet Fuel Testing 

Denver Jet Fuel

When it comes to jet fuel, what you cant see can hurt you.

Contaminated jet fuel causes engine flameouts, fuel gauge malfunctions, and other fuel system difficulties. In May 2019, a Cessna C550 on an air medical flight experienced a total loss of power in both engines because diesel exhaust fluid had been confused with de-icing fluid, which looks the same.

Because much of what contaminates fuel isnt visible with the naked eye, jet fuel testing ensures what goes into an airplane tank is only what should be there. Its a critical step, so you want to make sure you have it done right and done well.

When looking for a jet fuel testing company, the highest quality control standards are critical. Here are a few things to keep in mind as you consider your choices.

Follow The Correct Standards

Testing jet fuel works like any other kind of technical testing in that there are various standards to meet. These standards are set by several different groups for conventional jet fuel. you need standardized, world wide accepted testing that is very specific and acceptable to the jet fuel handling industry.

The most commonly used specifications and practices for Jet A or Jet A-1 include:

  • ASTM D1655 — US and international
  • UK Defence Standard 91-91 — UK and international
  • Joint Inspection Group Aviation Fuel Quality Requirements for Jointly Operated Systems — international
  • GOSST 10227 TS-1 — Russia and CIS
  • Number 3 Jet Fuel — China

For the most part, these standards are fairly similar because they deal with the same product. Minor variations in test limits can be dealt with by using the AFQRJOS checklist as it incorporates the strictest elements of ASTM D1655 and DEFSTAN 91-91.

Other specific standards deal with the more than 30 tests that might be done on your fuel, including checking sulfur levels, acidity, and freezing point, among others. You will also want to find out what standards the lab and its equipment are held to. 

ISO/IEC 17025 Accreditation 

States the lab operates competently and delivers valid results. That level of certification ensures your test results will have international approval.

Test The Right Stuff

Not only do you need a service that knows how to test jet fuel, but they also need to be testing that fuel for the right things. In some cases, the what and how of testing is handled by following standards, but its good to have a basic understanding of what you should expect a service to provide.

When you talk to a testing company, ask about how they stay on top of new issues that arise and require testing, such as discovering the DEF in the Ohio incident.

Contamination Sources 

The most common fuel contamination sources are water, particulates, surfactants & residues, and microbial growth.

While your fuel might have a low water content upon delivery, sitting around in storage provides ample opportunity for for water condensation to get in fuel. This could be rainwater leaks or damp outside air flowing in. Even a temperature change in the fuel itself can increase the chances of water condensing and changing the fuel makeup.

Particulates include dust and dirt, an inevitability despite new protective coatings on the interior surfaces of pipes and tanks. Airborne solids like dust and pollen or rubber from damaged hoses can also contribute to contamination.

Accidental contamination with DEF continues to be a possibility as changes to the standards for diesel vehicles at airports means it is on hand more. Another new contaminant being encountered is Fatty Acid Methyl Ester, which tends to show up when biodiesel fuel passes through a common fuel distribution system.

Microorganisms from air and water can get into the fuel and form solid debris that plugs fuel filters. The most common ones found are bacteria, yeasts, and fungi.

Fuel Types

Most commercial aircraft run on conventional turbine fuel called Jet A or Jet A-1. It comes directly from crude oil. Any testing company will be able to handle standard testing on this type of fuel.

Alternative fuels that are semi or fully synthetic have been added to the ASTM and DEFSTAN standards. More are on the horizon based on non-petroleum materials such as coal, biomass, and even algal growth. If youre considering a move to one of these fuels, you need a company that ensures its tests and procedures keep up with fuel innovation.

Experienced Jet Fuel Testing

Most of the time, there is no need for extreme speed on the part of your jet fuel testing service. But when you need it now, you need it now.

Cheap jet fuel testing can become problematic. You need a service that is open when you need them (including holidays!) and can perform tests now rather than later. A good service is going to be able to come on-site to pull samples for you and get them off for testing quickly.

The Final Word on Testing

An airplane engine is sensitive to any contamination in the jet fuel. Ensure your fuel product remains up to standards and safe for flying with proper jet fuel testing conducted at appropriate points along the supply path. The best testing services will be able to work with you and provide tests to the standards you require and to suit your timeframe.

If you are looking to add testing to your safety protocols, contact us to get a quote on our ISO accredited service.