These Audi V6 TDI engines can run on vegetable oil!

"With our strategy Head start 2030 we are pursuing the clear goal of launching new models worldwide from 2026 exclusively with electric drives. In doing so, we are making an essential contribution on the way to CO₂-neutral mobility,” says Oliver Hoffmann, Member of the Board of Management for Technical Development at Audi. “At the same time, we are optimizing our existing combustion engine portfolio towards greater efficiency and lower emissions. To this end, we are also creating the technical prerequisites for the use of sustainable fuels such as HVO.” Renewable fuels, so-called reFuels, offer the possibility of operating combustion engines in a more climate-friendly manner. They are a tried and tested means of defossilization – both in the short term and after 2033, when the last Audi with a combustion engine will roll off the assembly line in Europe.

Audi models with V6 diesel engines up to and including 210 kW (286 hp) that have been delivered since mid-February can fill up with so-called HVO fuel in accordance with European standard EN 15940. The name HVO derives from Hydrotreated Vegetable Oil, in English "hydrogenated vegetable oil". With this sustainable fuel, 70 to 95 percent CO₂ save compared to fossil diesel. Another advantage of HVO is its significantly higher cetane number, which ensures more efficient and cleaner combustion than conventional diesel. “The cetane number of HVO, which is around 30 percent higher, makes the engines more ignitable, which has a particularly positive effect on cold starts. We tested the effects on various components, performance and exhaust emissions in specific validation runs before approval was given," says Matthias Schober, Head of V-TFSI, TDI and PHEV Powertrain Development at Audi. The engine variants with the largest quantities were prioritized in order to give as many customers as possible the opportunity to use regenerative fuels.

Biological residues as a basis for HVO

Residual and waste materials are used in the production of HVO, such as used cooking oil from the food industry or residues from agriculture. With the integration of hydrogen (hydrogenation), the oils are converted into chain-shaped hydrocarbons. This means that the properties of the vegetable oils are adapted for use in diesel engines. They can be mixed with conventional diesel and thus replace fossil components, or they can be used 100 percent as pure fuel.

HVO is a so-called BTL (Biomass-to-Liquid) fuel. In addition to BTL, there are other manufacturing processes for synthetic diesel fuels, such as GTL (Gas-to-Liquid) or PTL (Power-to-Liquid). The latter can be sustainably made from renewable electricity, water and CO₂ be obtained from the atmosphere. The term XTL (X-to-Liquid) is used as a collective term for these fuels of the EN 15940 standard, with the X standing for a variable starting component. Pumps with the corresponding fuels are marked with this symbol. Approved Audi models have an XTL sticker in the tank cap.

HVO approval for numerous models

All V6 diesel engines with an output of up to and including 210 kW (286 hp) in the A4, A5, A6, A7, A8, Q7 and Q8 series that have been produced since mid-February 2022 can run on HVO fuel. The HVO approval for the Q5 takes place at the beginning of March, for the A6 allroad in the expansion stage up to 180 kW (245 hp)¹ in summer. At Volkswagen, the Touareg can be used in the 170 kW (231 hp) performance class.² and 210 kW (286 hp) fill up with sustainable diesel fuel.

In Europe, there is also approval for the 2021-cylinder diesel units in the Audi A4, Q3 and Q2 that have been built since June 3. In the models based on the modular longitudinal platform, the R4 TDI in the A4, A5, A6, A7 and Q5 series in Sweden, Denmark and Italy have been HVO-capable since the middle of last year, as market demand in these countries has not been is largest.

HVO diesel is already available at over 600 filling stations in Europe – most of them in Scandinavia, where environmental regulations are particularly strict. In Germany there are currently only a few filling stations that offer HVO - and the trend is rising. This is because the EN 15940 fuel standard is not yet part of the German fuel quality regulations (Ordinance on the quality and labeling of the qualities of fuels - 10th BImSchV) listed - in contrast to almost all other countries in the EU.

Compatibility of internal combustion engines with renewable fuels (reFuels)

With various pilot projects, such as the power-to-gas plant in Werlte, Audi has gained valuable insights into the production of sustainable fuels that are used throughout the Volkswagen Group. These experiences are also an important basis for the development of concepts for an overall sustainable energy system. The group works with mineral oil manufacturers and other energy suppliers and contributes its technical expertise to ensure that existing engines are compatible with reFuels.

Since March 2021, for example, environmentally friendly R33 Blue Diesel has been used at Audi factory filling stations in Ingolstadt and Neckarsulm. This diesel has a renewable content of up to 33 percent, based exclusively on residual and waste materials. R33 has two major advantages: On the one hand, it saves at least 20 percent CO₂ compared to fossil diesel in the well-to-wheel balance analysis. On the other hand, it is a premium fuel that has a positive effect on wear and service life thanks to special additives. R33 Blue Diesel meets today's EN 590 standard and is therefore approved for all diesel vehicles, including older ones. The Volkswagen Group played a key role in the development of the fuel and contributed to its marketability with its expertise. In addition to the Audi and Volkswagen factory petrol stations, the fuel is already available at a number of public petrol stations. The standard in Germany, however, is still fossil diesel fuel with up to 7 percent biodiesel, which is marked with the symbol "B7" at filling stations. The R33 Blue Gasoline fuel for petrol engines will also follow shortly – the petrol counterpart to the R33 Blue Diesel. Like the environmentally friendly diesel fuel, it can be used in the entire existing fleet. For the future, Audi and the entire Volkswagen Group plan to release further combustion engines for renewable synthetic fuels and will thus contribute to defossilization. Photo credit: Audi