The overall quality of diesel fuel is dependent on a number of factors. These include BTU value, viscosity, pour flow point, aromatic and paraffinic content, and resistance to contaminant buildup such as water and bacteria. A diesel fuel’s quality also is very dependent on its cetane number.
The cetane number (CN) is an index of the ignition point or combustion quality of diesel fuel and is measured using an ASTM D613 test. Standard European BS EN590 diesel from the pump normally has a minimum cetane number of around 51, with premium pump diesel a little higher. Depending on engine design, driving conditions, and so on, the optimum cetane value for most vehicles is around the mid to high 50s. Any value greater than 60 will not achieve any additional benefits and in most cases will alter ignition timing to the degree that power is lost.
Matching cetane to the engine is important in order to maximise the engine’s performance. Biodiesel fuels in particular, especially the homemade brews, usually start with a much lower cetane number so cetane improvement for these fuels is essential.
A fuel with too low of a cetane number for a particular engine will result in reduced cold-start ability, rough running, excess engine noise/vibration and reduced combustion quality. This leads to reduced performance, excess emissions, and carbon buildup throughout the engine and emission system components (intake, EGR, DPF, etc.)
A higher cetane fuel that is a proper match for the engine will reduce ignition delay, improve overall combustion quality, liberate more BTU (energy) from the fuel, and improve performance and MPG. It also will reduce engine noise, deposit buildup, and exhaust emissions.
What should I look for in a cetane booster?
Contrary to some propaganda, alkyl nitrates still offer the greatest improvement in cetane number, with measured increases of up to eight points. When it comes to alkyl nitrates, 2-ethylhexyl nitrate (2-EHN) is the most popular and most respected. It offers more consistent ignition quality whilst reducing unwanted and negative combustion conditions.
Fuel additive manufacturers recognise both the benefits of boosting the cetane number and using 2-EHN so much now that most offer cetane improvers. The question in this case is what are you getting for your money?
From close examination it appears many cetane boosters contain useless fillers. To maximise profits most manufacturers still insist on the single bottle per tank philosophy. Some 200-300ml bottles that treat a single tank of fuel have as little as 20% active ingredients. This is lucrative for the manufacturer but not a good value for the consumer. Therefore, it is important to understand what you are getting for your money.
The optimum amount of 2-EHN is around 20-100ml per tank of fuel, depending on the engine and base cetane level. As 2-EHN can reduce lubricity it is important that a lubricant is also blended in. To ensure you are getting the best value, make sure the product contains 2-EHN as its base and a reasonable proportion of the remainder contains useful ingredients, such as lubricant, detergent, etc.
So what do we recommend and why?
Active cetane improvers are essentially a form of fuel modification, or more accurately, combustion modification. However, when combined with the correct fuel catalyst technology, latest nano detergents, and lubricity additives, they can turn the most mediocre pump fuels and biodiesels into super diesel that will outperform the best premium pump fuels.
Archoil® achieved this with its new AR6900-D MAX. Rather than introduce another diluted cetane booster, they decided to release a concentrated chemistry product that contains 100% active ingredients. It provides optimum increases in cetane whilst being able to treat multiple tanks of fuel, rather than just one.
Archoil also added their patented fuel catalyst technology to improve combustion quality even further. It contains an optimum amount of 2-EHN with the remainder composed of the aforementioned catalyst, a synthetic lubricant that protects the entire fuel system against the harmful effects of low lubricity, low sulphur fuels, and carefully selected detergents that safely remove fuel system and carbon deposits. This results in an optimum combustion condition, comprehensive fuel system protection and cleaning, performance increase, and reduction in harmful exhaust emissions.
Archoil’s AR6900-D MAX offers the greatest value for the customer. At last, a complete and fully concentrated additive package that is a much better value than its competitors, but more importantly, much less expensive per tank than upgrading to premium diesel at the pump.