When you pull your vehicle up to the fuel pump, there are usually a few options to choose from.  Various octane levels of gasoline, perhaps an E85 ethanol blend, and lastly a diesel option.  Most vehicle owners know what octane level their vehicle should use, whether that’s a low, medium or high grade.  But if you have a diesel, do you what cetane number your fuel contains?  Do you know what cetane rating really indicates?

What is the Cetane Rating for Diesel Fuel?

Most vehicle owners know about octane in their gasoline.  The higher level of octane indicates a gasoline’s ability to resist pre-detonation, or combusting too soon.  The cetane rating in diesel fuel indicates a similar relation to combustion.  But higher numbers indicate they are more likely to ignite with a shorter ignition delay rather than resist combustion.  In the case of diesel cetane, higher is better for efficiency and complete combustion in the engine cylinder.  The cetane number in an important factor is indicating a fuel’s quality.  However, energy content, density, lubricity, cold-low properties, and Sulphur content also contribute to indicate quality in a diesel fuel.

What is the Typical Rating for Cetane in Diesel Fuel?

The typical cetane in most diesel will vary based on geographic location and time of year.  North American refineries mostly adopt ASTM D975 as their diesel fuel standard.  They set the minimum cetane number to 40, with typical values at your local fuel pump in the 42-45 range. Some stations will also offer a premium diesel fuel, but it may not have a higher cetane rating.  If it does, it will have an additive to improve the cetane number.  It will most likely have additives to improve lubricity, more detergents to clean the fuel injectors and minimize carbon deposits, and increased water dispersants.  California requires their diesel fuel to have a minimum cetane of 53.  Likewise, Texas requires 110 counties in their state to use a minimum cetane of 48 or greater, but most other states follow the guide of a minimum of 40.

North American diesel doesn’t exactly match the rest of the world.  Europe has used a different index than the ASTM standard and currently uses a minimum rating of 51.  In the past, cetane rating was as low as 38 in the mid-1990s and was increased to 40 in the year 2000.  In some areas of Europe you can also find a premium diesel with a cetane rating of 60.  Finland has unique filling stations that offer a typical cetane rating of 63 with a select few of renewable diesel options in the 70 range.  They are among the highest in the world right now.

Why Are There Different Cetane Levels Available?

You might begin to ask the question of why there are different cetane levels available across the United States, and especially around the world.  Diesel engines operate well with a cetane rating of 48-50, yet many fuel pump stations will only offer a diesel fuel with a cetane rating or 45 or less. The reason comes down to simple economics.  Your diesel engine will run fine with a lower cetane level, perhaps not at optimum levels, but well enough that most consumers would not pay more for a higher cetane fuel.

How Can I Get Higher Cetane Levels If Not at the Pump?

Some communities offer biodiesel options that aren’t available in all markets across the United States.  Biodiesel from vegetable sources typically range from 46 to 52, and animal-fat based biodiesel range in cetane from 56 to 60.  Dimethyl ether can be produced as a biofuel with a higher cetane rating of 55 to 60, and diethyl ether can also be used as a diesel fuel but it also has lubricity issues that can be a concern.

If you don’t have access to any of those options in your local community, your next best option for higher cetane is to use an additive in your diesel fuel.  AMSOIL offers Diesel Cetane Boost, which can increase cetane level up to 8 points in an 80-gallon fuel tank.  If your diesel runs best with a cetane level of 50, an additive can economically increase the offering from your local fuel station for optimum performance, low emissions, and maximum power.

Wrapping Up

Just be aware that adding cetane beyond what your engine manufacturer recommends doesn’t necessarily mean you’ll see a big jump in returns.  In the case of cetane, more doesn’t always mean better.  If your diesel engine was designed to run best at a cetane level of 48, paying extra at the pump for a diesel fuel with a cetane level of 60 isn’t going to be worth it.  Only increasing cetane to the optimum level, or slightly above, the manufacturer recommendation is suggested.

It’s pretty easy just pull up to the pump, grab the green handle for diesel, and put it in your tank without thinking too much about cetane.  Your diesel engine will run on what is offered at the pump, whether that is optimum for your engine or not.  You may find that adding cetane up to the manufacturer recommended level offers better performance, fuel mileage, and reduced maintenance in the long run.  Adding AMSOIL Diesel Cetane Boost is just part of an overall plan to keep your diesel running well.  If you need help with determining a complete maintenance plan for your vehicle, your local AMSOIL dealer at Buy Great Oil is here to help with a complete package of products and hints to make the job easier.