However, almost all truck manufacturers still require very short engine oil changes when running on biodiesel. Old findings relating to running engines on rapeseed oil, which at the time was still pure and not esterified, indicate that when using B100 engine oils should be changed after one-third of the usual mileage (usually 30,000km instead of 100,000-120,000km). But are the arguments in favour of short oil usage periods valid? Could the lubricants be used longer? OELCHECK gets to the bottom of these questions and closely monitors the used engine oils from the B100-powered vehicles at Johann Dettendorfer Spedition.
Johann Dettendorfer Spedition is one of the top 100 German logistics companies. Many international awards attest to the achievements of this traditional, owner-managed company. Its headquarters are in Inntal, Bavaria, directly on one of Europe's major north-south axes. There are further locations in Italy, Poland and several German federal states.
Johann Dettendorfer Spedition was founded in 1825. Today, the core competencies of the company include comprehensive warehousing and logistics services in addition to goods transport. The trend is increasingly towards integrated service solutions. Johann Dettendorfer Spedition’s customers benefit from the company’s expertise, innovation, modern fleet and intelligent IT concepts. These perfectly meet the requirements of Industry 4.0, with its IT-focused way of working. This ensures deliveries to customers are not only just-in-time, but also just-in-sequence. The Dettendorfer branch at Deizisau in Baden-Württemberg, for example, delivers liquid aluminium to the processing plant at the specified time and in the appropriate quantity at a temperature of 700 °C using special trucks. Transporting and storing raw materials and disposing of foundry waste are also part of the freight forwarder's service package.
The aim is to operate the fleet economically and ecologically. Management has been demonstrating for years how well these aspects, which at first glance might seem contradictory, can be reconciled:
Biodiesel or FAME (fatty acid methyl ester) can be used in pure form (B 100) in diesel engines if approved by the vehicle manufacturer. The fuel consists of re-esterified vegetable oils.
In Germany, it is almost exclusively based on rapeseed oil. Hence it is also called RME (rapeseed methyl ester). DIN EN 14214 sets out the minimum requirements for biodiesel. However, the freight forwarder’s specifications go far beyond this. For example, the total contamination of the fuel may only be 10 mg/kg instead of the 24 mg/kg required by the DIN standard. And instead of a maximum water content of 500 mg/kg, Dettendorfer only accepts 250 mg/kg. After all, water not only causes corrosion and wear and tear; excess water content also makes biodiesel susceptible to microbial growth.
Since biodiesel ceased to enjoy favourable tax treatment in Germany in 2008, filling stations in Germany have become rare. Abroad, however, it is still cheaper than obtaining fossil diesel fuel from petroleum. This is clearly reflected in the operating costs of the fleet. After all, the tank of a large truck can hold up to 1,300 litres of fuel. As far as possible, refuelling takes place at one of the company's own truck stops in nearby Austria, thereby benefiting from favourable tax treatment.
However the quality of the RME, which is monitored by OELCHECK taking random samples, has to meet the high requirements of Johann Dettendorfer Spedition. All other customers who fill up while travelling in their environmentally friendly trucks or cars also benefit from this. The Dettendorfer Group's Austrian truck filling station on the A12 in Inntal, Austria, is particularly popular with truckers. The free Truck Checkpoint is located here. Total weight and axle load are checked and tyre pressure and tread depth measured in just 15 seconds. These are important criteria that affect truck road safety as well as reducing fuel consumption and carbon emissions.
Johann Dettendorfer Spedition's vehicles are powered by pure biodiesel. This brings economic and, above all, ecological advantages. But there is also a drawback: most vehicle manufacturers recommend engine oil changes after 30,000 km rather than 100,000 km when trucks run on biodiesel. And this not does not just mean considerable additional costs! The engine of a single 40-ton truck uses approximately 40 litres of engine oil. Changing the oil and oil filter takes about two hours, and the vehicle is not available during this period. In addition, significantly more fresh oil is consumed and correspondingly more waste oil is produced. The total cost of an oil change is about 500 €, which eats up a large part of the fuel costs saved again.
This high consumption of engine oil goes against the philosophy of Johann Dettendorfer Spedition, which is to use all resources sparingly. However, engines are also supposed to be operated safely and sustainably and achieve the longest possible service life. This is why engine oil is replaced after a short period of 30,000 km, in line with the specifications of MAN.
Specification of shorter oil-change intervals is based on past experience. It has been more than 10 years since it was discovered that using the biodiesel quality available at the time led to increased entrainment of fuel into the engine oil. At the time, laboratory tests were only carried out on engines for agricultural vehicles fitted with the engine technology of that period. Unfortunately, there are no more recent long-term studies into the condition of used engine oils from commercial vehicles with a modern generation of engines and using more refined biodiesel.
In general, for both biodiesel and fossil fuels, viscosity decreases if too much fuel penetrates an engine oil. The engine oil becomes thinner, lubrication performance decreases and there is a risk of engine wear.
If biodiesel is used, this oil dilution may occur to a greater extent because the fuel does not burn completely. This is due to the physical properties of the fuel. Fossil diesel has a flash point of 55 °C or slightly higher, but the flash point of biodiesel is usually well above 100 °C. The permissible minimum under DIN EN 14214 is 101°C. Conventional diesel in engine oil evaporates at an oil temperature of roughly 80 °C, whereas biodiesel only does so to a limited extent. Uncombusted biodiesel can make the engine oil increasingly thinner. The risk of engine damage increases accordingly. If too much biodiesel is left in the engine oil, some of its incompletely esterified components can lead to greasy or even solid deposits in piston ring grooves or on the piston head and shorten the engine service life.
Unfortunately, OEMs do not specify a maximum value for the proportion of biodiesel in engine oil. OELCHECK regards entrainment of over 6 % as critical for modern SAE 5W-30 low-friction diesel oils. This figure is based on the large number of used oil analyses from newer vehicle engines operated with biodiesel B7, B10 or B100.
Are the shortened oil service life times prescribed by almost all vehicle manufacturers pure prevention or real necessity? Johann Dettendorfer Spedition started a preliminary study together with OELCHECK to find out more about the condition and performance of engine oils.
OELCHECK has been monitoring the engine oils of three vehicles belonging to the freight forwarder since spring 2020. In order to take into account as many operating conditions as possible, OELCHECK is examining the oils from a long-haul truck that operates on a two-shift system, a silo vehicle with a compressor and a truck used for regional transport. The engines use SAE class 5W-30 low-SAPS engine oil approved by the vehicle manufacturer. This has a synthetic base oil, meets international specifications and is approved for use in EURO V and VI engines by all well-known vehicle manufacturers.