One thing that sets apart a good tank servicing or fuel polishing partner from a no-so-good one is their familiarity with fuel testing. The better partners in this area should incorporate ASTM testing into their service protocols, because their goal will be to make sure their customers (you) know everything they need to know to make the best decision possible.
ASTM testing of stored fuel is the best way to assess exactly how good or bad condition the fuel is in. And ASTM fuel testing after servicing is the best way to document for sure how fuel servicing has benefitted you (or not). It's really the ONLY way to reliably do either of these.
What is ASTM?
You’ll hear the name ASTM referenced many times within the industry. The American Society for Testing Materials is a broad organization that has developed accepted test standards in virtually every area you can think of, not just for fuel. There's a standard for steel fibers that go into concrete. There's a standard for how to prepare plastic surfaces for electroplating. A standard for defining how to conduct abrasion tests involving wet sand and rubber wheel. And of course, there are standards for defining the properties of any kind of petroleum fuel you want to look at.
ASTM develops the testing methods to address a given question, through collaboration with industry leaders. The required results of the tests (the standard to b met) are usually agreed upon by the members of the industry itself - for example, the minimum lubricity standard for diesel fuel has been defined through consensus that was heavily influenced by engine manufacturers who know what's needed to make their products (engines) last longer. ASTM itself doesn’t have any ability to enforce anything – they just develop the standards and how to measure them. But it is their standards that are referenced and required by outside organizations like the Federal Government that do have the ability to enforce them. So when the government says that biodiesel fuel has to meet 7 different ASTM standards or it can’t be called biodiesel, now the standards have teeth.
What Do These Tests Mean?
The specifications for fuels like diesel and biodiesel are defined by the results of different numbered ASTM tests. These tests all mean somethign important - each measures an important property of the fuel, a property that’s been determined to be relevant to the fuel doing what it needs to do. You’ll usually hear the standard referenced by a number and a test name.
A good fuel servicing partner may not coordinate all of these tests – they’re not always needed every time. But they should be able to facilitate getting them if needed.
Flash Point (D93) – this test determines at what temperature the fuel vapors will ignite. If the fuel doesn’t meet a minimum flash point, it won’t burn properly in an engine. Since fuel has to burn for an engine to run, it's important that this property be satisfactory. If the fuel is contaminated with something (like gasoline contamination of diesel), it will show up in a skewed flash point.
Cloud Point (D5773) – one of the cold weather property tests for fuel, this defineds the temperature at which the fuel becomes cloudy due to wax crystals dropping out of solution. This is important to know because, for most fuels, there’s about a 10 degree (F) difference between the cloud point and the lower temperature at which the fuel gels up enough to shut the engine down, itself defined by a different test, the Cold Filter Plug Point (D6371).
Water and Sediment (D2709) – one of the tests specified by governing agencies to be done by mission critical agencies who store emergency fuel. This test simply measures the water and sediment content of the fuel. If it’s too high, it can damage equipment and causes corrosion of storage systems. Water and sediment content is also something measurable that should change with fuel polishing (i.e. fuel polishing should take fuel high in water and sediment and remove those contaminants).
Microbial Contamination – there are several tests, such as microbe count, that can specifically judge the number of microbes per unit of fuel. A good fuel polisher will use a biocide in their process, so this test should be run on the finished fuel to confirm that the biocide worked as needed.
Cetane Number – stored diesel fuel needed adequate cetane rating in order to run properly in diesel engines. There is a cetane number test and also a cetane index, which is a calculation based on the distillation value of the fuel combined with its density or API index (another way to state density).
If you’re storing B99 biodiesel, there are also other tests (acid number, glycerin content, sulfated ash, rancimat) that you or your fuel partner should be running to document that the fuel you’re using and storing is in proper working order.
If your fuel servicing partner isn’t running these tests or can’t help you get them done, you should consider a different partner if possible.
You may be interested in these related posts:
- Storing fuel without periodic testing: Playing with fire
- "Wow" Facts on Contaminated Diesel Fuel. Be Prepared.
- Fuel contamination symptoms: a quick primer
This post was published on April 25, 2016 and was updated on March 1, 2023.