Diesel fuel quality

Diesel fuel quality

Those who travel overland outside the ‘western world’ have to deal with poor quality diesel fuel. Although the 70 / 80’s diesel engine in most overland trucks can easily cope with low quality diesel,  modern diesel parking heaters do not. A bit about diesel fuel quality.

Diesel fuel quality

Poor diesel quality is often associated with the obvious pollution with sand, water, oil and other impurities. But there is more to it than diesel fuel impurity.

Diesel Fuel Quality - different diesel samples
Diesel fuel samples - all within EN590 specification

Diesel fuel can simply be outside EN590 specification - the standard for commercial diesel fuel in the 'western world'. The main diesel quality indicator, the diesel cetane number (diesel ignition index) can be too low.

Nonetheless, older diesel engines easily run on low cetane diesel fuels, only mileage / fuel economy might be affected. But for diesel parking heaters it's different.

Diesel fuel - cetane number

Modern diesel parking heaters made by Eberspächer and Webasto are known to be much more sensitive to diesel cetane level fluctuations. Even normal diesel fuel might cause ignition failures in diesel parking heaters - more about this below.

Here's the diesel fuel specification for a Eberspächer Airtronic D3 / D4, requiring DIN EN590 diesel fuel;

Diesel fuel specification Eberspacher Airtronic D3 and D4
Diesel fuel specification for Eberspacher Airtronic D3 and D4

Parking diesel heaters are often used in ships running on 'Gas Oil' or 'red diesel''. Nowadays Gas Oil also meets EN590 specification to adhere to low sulphur regulations. There's no significant difference (anymore) between Gas Oil and commercially available diesel in Europe.

Diesel parking heater ignition problems

Our old 1990’s Eberspächer D3L already encountered diesel fuel far outside EN590 specification with Iranian diesel from 70’s refineries. The diesel simply failed to ignite, specially at colder temperatures. And it can get really cold in Iran and Turkey!

So what if there’s no EN590 diesel fuel available and its really cold? A modern diesel parking heater may fail due to low cetane levels. Here’s what Eberspächer suggests;

Diesel fuel quality specification Eberspacher Airtronic D3 and D4
Diesel fuel quality specification for Eberspacher Airtronic D3 and D4

In rare occasions even commercially available EN590 diesel fuel can fail to ignite in modern parking diesel heaters - due to low cetane levels.

Note : Heating oil ( DIN 51603) is also known as "Fuel oil - class number 2" and roughly matches EN 590 diesel fuel.

Diesel fuel with low cetane levels

Those running diesel parking heaters on gasoil (red diesel) may experience ignition failures due to low cetane levels.

In Ebespächer’s technical bulletin No 281 (Nov 2007) highlights the cause how diesel fuel can have a low cetane level;

Gas oil will start to degrade after approximately 6 months this is where the heavy molecules start to separate in the fuel and begin to sink to the bottom of the tank to form 'sludge', water will also start to separate from the fuel and collect with the water generated by condensation. The cetane value of the fuel will begin dropping. This is starting to happen before it leaves the refinery, then it sits in the depots tank until it is transferred to the boats tank. That is normally the last time that the fuel will get mixed or shaken because unlike sea boats or road vehicles the inland waterways tend to be calm the fuel is allowed to sit and separate.

Those with overland vehicles parked for many months can experience the same issue with commercially available EN590 diesel. Solution? A short drive mixes the cetane number back to normal.

Diesel fuel Cetane number explanation


Diesel fuel information and more

Diesel fuel EN590 specification

Diesel fuel cetane index number

Fuel oil

Heating oil

Eberspächer technical bulletin No 281