RUDN University: Diesel Engine Modified to Run on Rapeseed Oil

Engineers in a Russian research project have reworked a conventional diesel engine so that it can run on rapeseed oil instead of standard diesel. The findings are fuelling the argument that internal combustion engines powered by biofuel may be far from finished-and raising questions about what that could mean for the continued rise of electric cars.

What the researchers achieved

Engineers at RUDN University examined an ordinary diesel engine of the sort widely used in commercial vehicles. Rather than filling it with regular diesel, they used rapeseed oil-a vegetable oil produced in large volumes across Europe and familiar from supermarket shelves.

The key challenge is straightforward: pure vegetable oil is much thicker and harder to ignite than diesel. In practice, that typically means poorer atomisation in the cylinder, more incomplete combustion, higher consumption and increased pollutant output. The research team set out to remove these drawbacks through engineering changes.

"Through targeted changes to injection timing, the injector nozzle and the fuel system, the engine running on rapeseed oil approaches the performance and efficiency of a classic diesel."

The test results indicate that, with the right calibration, an engine can be adapted so rapeseed oil is not merely an unusual stopgap, but a credible fuel option.

How a diesel engine can run on rapeseed oil at all

The key technical levers inside the engine

In essence, the researchers focused on three areas:

• Injection timing: The start of injection was brought forward to give the slower-to-evaporate rapeseed oil more time to vaporise.
• Injector nozzle: The nozzle geometry was modified to generate finer droplets and distribute the oil more effectively in the combustion chamber.
• Fuel system: Pressure and delivery rate were optimised so stable operation remains possible despite the higher viscosity.

With these measures in place, typical vegetable-oil disadvantages were reduced noticeably: the engine ran more smoothly, power output stayed closer to diesel levels, and the additional fuel consumption fell.

The challenges of vegetable oil in the tank

Rapeseed oil does not work in an engine without drawbacks. The researchers highlight several technical hurdles:

• Poor atomisation: Thick oil forms larger droplets, which worsens combustion.
• Higher consumption: Per kilowatt-hour of output, the engine generally needs slightly more fuel.
• Exhaust quality: Engines that are poorly set up produce more soot and unburnt hydrocarbons.

These were precisely the points the team investigated on a test bench. Using measurement data, the engineers were able to counter the rapeseed oil “weak spots” in a targeted way and improve operation step by step.

What this means for the environment and climate

Biofuel instead of fossil diesel

Rapeseed oil is classed as a first-generation biofuel. During growth, the crop absorbs CO₂, which is then released again when the fuel is burned. On a balance basis, this can make it considerably more climate-friendly than fossil diesel-provided cultivation is done sustainably.

The study points to several environmental advantages:

• reduced dependence on fossil raw materials
• a fuel that can be produced regionally, especially for agriculture
• potential for lower emissions of nitrogen oxides and carbon monoxide with optimised settings

"The decisive point: it is not the fuel alone that determines the exhaust gases, but the interplay between biofuel, engine control and injection technology."

When tuned correctly, certain pollutants decrease, while the CO₂ balance is clearly improved compared with conventional diesel. That makes rapeseed oil an interesting transitional option for heavy transport and agricultural machinery.

Where rapeseed-oil diesel would make the most sense

In the urban car market, many countries are politically committed to electric powertrains. In other segments, the picture is different:

• Agriculture: Tractors and harvesters have long duty cycles, often operate far from rapid-charging infrastructure, and could be refuelled directly with locally produced rapeseed oil.
• Construction equipment: Excavators, wheel loaders and generators on building sites could run on biofuel where batteries hit practical limits.
• Long-haul transport: For heavy lorries over long distances, liquid energy carriers still offer advantages, particularly in low temperatures.

In areas where batteries would need to be extremely large, expensive and heavy, an optimised diesel engine running on biofuel can play to its strengths.

Does this mean the end of electric cars?

Electricity versus biofuel-two systems compared

Electric cars score highly for efficiency, zero local tailpipe emissions and falling battery costs. A rapeseed-oil diesel, by contrast, offers benefits in range, refuelling time and the ability to use existing infrastructure. For that reason, the rapeseed-oil approach is less an “EV killer” and more a complementary pathway for applications where electrification remains difficult today.

Aspect	Electric car	Rapeseed-oil diesel
Drivetrain efficiency	very high	significantly lower
Range / refuelling time	depends on charging power	long range, fast refuelling
Infrastructure	charging points required	existing filling stations usable
Typical use	city driving, commuters, many cars	agriculture, long-haul, off-road

For mass-market private cars, the direction of travel remains clearly towards electric power. This innovation does not fundamentally change that, but it reinforces the idea that combustion engines may still have a role in niche applications for longer.

Why the research could still be a game-changer

The technical work demonstrates that established engine platforms do not automatically have to be scrapped. With manageable effort, manufacturers could:

• update older engine families to run on biofuels
• develop hybrid systems combining electric drive with biofuel diesel
• make commercial vehicles “greener” more quickly in regions without a stable electricity mix

For countries with limited charging infrastructure but strong agricultural potential, this outlook is particularly appealing. It enables climate progress without requiring the entire transport system to be rebuilt in a short period of time.

Open questions: land use, prices, long-term technical effects

However compelling the results sound, several issues remain unresolved:

• Competition for land: Every additional rapeseed crop needs land, water and fertiliser. How much growing area should be used for fuel instead of food is politically sensitive.
• Costs: Engine conversion, injector-system maintenance and biofuel production all affect the price at the pump.
• Long-term durability: Vegetable oils can gum up lines and nozzles if engines are not used regularly or are set up incorrectly.

The researchers themselves frame their work as a step towards optimised biofuel blends. In future, mixes of rapeseed oil, diesel and other additives could become standard to strike a compromise between climate impact, engine protection and efficiency.

What drivers and farmers can take from this now

For the typical car driver, little changes in the short term. In Europe, manufacturers are clearly prioritising EV models or hybrids for new vehicles. Over the longer term, however, hybrid systems using biofuel diesel could appear in niche areas-for example in large SUVs or light commercial vehicles-so long as there is still demand.

The development is more immediately relevant for organisations operating fleets of diesel vehicles:

• Farmers could, in future, produce part of their fuel from their own crops.
• Hauliers in rural regions would gain another option alongside HVO, LNG and, later, hydrogen.
• Local authorities could transition municipal fleets gradually to adapted biofuels.

For policymakers, the study underlines that the “EV or combustion engine” debate is too narrow. Alongside batteries and hydrogen, modern biofuel is emerging as another piece of the puzzle. A realistic transport transition will likely end up as a mix-and this rapeseed-oil research adds one more component to that picture.