Yes—cars have run on vegetable oil, from Diesel’s peanut-oil demo to today’s biofuels

Yes. Since the dawn of the diesel engine, vegetable oils have powered vehicles—first as straight plant oils in demonstrations and wartime improvisations, then as refined biodiesel and today as “drop‑in” renewable diesel made from vegetable oils and fats. The practice ranges from early 20th‑century experiments to modern, standards-compliant fuels used in millions of diesel vehicles and fleets.

How it started: a brief history of vegetable oil in engines

From its earliest days, the diesel engine was tied to plant oils. Rudolf Diesel’s famous demonstration in 1900 ran on peanut oil, and he foresaw farmers making fuel from their own crops. Over the following century, fuel shortages and environmental concerns periodically revived interest in vegetable oils for transport.

The timeline below highlights the key moments when vegetable oils met the road.

• 1900: At the Paris Exposition, a diesel engine is publicly demonstrated on peanut oil, proving plant oils can power compression-ignition engines.
• 1911–1912: Diesel writes that vegetable oils could become as important as petroleum for engine fuel, especially in agrarian economies.
• 1940s: During wartime fuel scarcity, plant oils see limited, local use in tractors, trucks, and stationary engines; most deployments are improvised and short-term.
• 1970s: Oil shocks spur research. Germany’s Elsbett develops engines optimized for vegetable oils; hobbyists begin “straight vegetable oil” (SVO) conversions.
• 1990s–2000s: Biodiesel (a chemically processed fuel from vegetable oils/animal fats) gains standards (ASTM D6751, EN 14214) and commercial traction; waste-oil “greasecar” conversions draw public attention.
• 2010s–2020s: Renewable diesel (HVO), a hydrotreated, drop-in diesel made from vegetable oils/fats, expands rapidly in the U.S. and EU, fueling municipal and commercial fleets at up to 100% blend.

Taken together, the record shows a long arc: from proof-of-concept with straight plant oils to mainstream, standards-compliant bio-based diesels at scale.

Three ways “vegetable oil” fuels reach the tank

Not all plant-oil-based fuels are the same. The term “vegetable oil” gets used loosely, but the engineering—and what your vehicle can safely use—differs significantly.

Straight Vegetable Oil (SVO/WVO)

Unmodified or filtered/fined cooking oil (new or “waste” from fryers). Some enthusiasts run older diesel engines on SVO using heated, dual-tank systems to solve cold-start viscosity issues. It is not a standardized road fuel, and unmodified use often violates fuel-tax and emissions rules. High viscosity risks coking injectors, ring sticking, and pump damage if not properly heated and managed.

Biodiesel (FAME)

Produced by transesterifying vegetable oils or animal fats with methanol and a catalyst, yielding fatty acid methyl esters (FAME). Meets ASTM D6751 (U.S.) or EN 14214 (EU) when made correctly. Sold pure (B100) or blended with petroleum diesel (B5, B20). Many OEMs approve blends up to B20 if the fuel meets ASTM D7467. Biodiesel has higher cetane and better lubricity but slightly lower energy content and can raise NOx in some legacy engines.

Renewable Diesel (HVO)

Hydrotreated vegetable oil and fats refined into paraffinic diesel chemically similar to petroleum diesel. It meets diesel specs (ASTM D975 in the U.S.; EN 15940 paraffinic spec in Europe) and can be used at up to 100% (R100) in many modern diesel engines without modification. It has very high cetane, excellent cold-flow properties (depending on cut), and typically reduces both PM and NOx versus conventional diesel.

Where it’s used today

Plant-derived diesel fuels are mainstream in multiple markets, with different labels and limits depending on the fuel and region.

Here are common real-world uses and approvals as of 2025.

• U.S. retail diesel commonly contains up to 5% biodiesel (B5) without special labeling under ASTM D975; B20 pumps are widespread in the Midwest and selected states.
• EU road diesel typically allows up to B7 under EN 590; many countries blend at or near that level nationwide.
• Renewable diesel (HVO/RD) is widely used by fleets in California, Oregon, and parts of Europe, often at R99/R100. Suppliers include Neste, Diamond Green Diesel (Valero/Darling), Eni, and TotalEnergies.
• OEMs: Many North American light- and medium-duty diesels from Ford, GM, and Ram, and heavy-duty engines from Cummins and others, allow up to B20 that meets ASTM D7467; HVO is treated as regular diesel if it meets ASTM D975/EN 15940. Always check the vehicle’s manual and regional fuel standards.

The net effect is that, while straight cooking oil remains niche, refined fuels made from vegetable oils are a routine part of the diesel supply in multiple regions.

Why straight cooking oil isn’t a drop-in fuel

Running an unmodified car on grocery-store oil is a persistent myth. The engineering challenges are real and can be costly if ignored.

Key technical hurdles include the following.

• Viscosity: SVO is far thicker than diesel, especially when cold, leading to poor atomization, incomplete combustion, and carbon buildup.
• Cold-flow: High pour point causes gelling; dual-tank, heated systems are typically required to start and switch over.
• Injector and pump stress: Rotary/inline pumps can be damaged by high-viscosity fuel; modern high-pressure common-rail systems are especially sensitive.
• Deposits and durability: Unburned triglycerides can polymerize, gumming rings and injectors and contaminating oil.
• Regulatory issues: Most jurisdictions require road fuels to meet standards and pay fuel taxes; raw waste oil usually doesn’t qualify.

These constraints are why industry and regulators coalesced around standardized biodiesel and renewable diesel rather than raw plant oils for road use.

What it takes to run SVO legally and safely

A minority of enthusiasts still operate older diesels on SVO/WVO, but it involves careful engineering and compliance steps.

Typical requirements look like this.

• Appropriate platform: Older, mechanically injected, indirect-injection diesels (e.g., 1980s–90s Mercedes, certain agricultural engines) tolerate SVO better than modern common-rail systems.
• Heated dual-tank kit: Start and shut down on diesel; switch to hot SVO only when coolant has warmed the fuel; purge before shutdown.
• Fuel preparation: Settle, filter, and dewater waste oil; verify free fatty acids and contaminants are within safe limits.
• Maintenance discipline: Shorter oil-change intervals; regular injector and combustion-chamber inspections.
• Legal compliance: Observe local rules on road-fuel taxation and emissions; in many places, only standardized biodiesel/renewable diesel qualifies as legal road fuel.

Even then, owners accept increased maintenance risk; for most drivers, standardized bio-based diesel fuels are the practical route.

Environmental and economic picture

Vegetable-oil-derived fuels aim to cut petroleum use and greenhouse emissions, but outcomes vary with feedstock and processing.

Consider the major trade-offs.

• GHG emissions: Biodiesel often shows 50%–80% lower lifecycle CO2e than fossil diesel; renewable diesel can reach similar or higher reductions. Waste-oil feedstocks generally score best; food-crop oils can be more variable due to land-use impacts.
• Tailpipe emissions: Biodiesel reduces PM, CO, and HC; older engines sometimes see slight NOx increases. Renewable diesel typically reduces both PM and NOx.
• Performance: Biodiesel has ~8%–12% lower energy content per liter; HVO is closer to fossil diesel and often improves ignition quality (high cetane).
• Cost and availability: Prices track policy credits (e.g., U.S. RFS, LCFS) and feedstock markets; supply has expanded, particularly for HVO in North America and Europe.

In short, the biggest environmental gains come from using waste and residue oils at industrial scale and meeting robust fuel standards.

Bottom line

Vegetable oil has indeed powered cars—from Diesel’s peanut-oil showcase to modern fleets running on biodiesel and renewable diesel. While pouring straight cooking oil into an unmodified car is neither wise nor legal in most places, refined fuels derived from vegetable oils are now a normal, standards-compliant part of the diesel landscape.

Summary

Yes, cars have used vegetable oil: historically as straight plant oils in demonstrations and emergencies, and today predominantly as standardized biodiesel (FAME) and renewable diesel (HVO) produced from vegetable oils and fats. Modern diesel vehicles commonly use low to moderate biodiesel blends and, increasingly, 100% renewable diesel, while straight vegetable oil remains a niche, high-maintenance approach suited to specific older engines and subject to legal and technical constraints.

Can vegetable oil be used in a car?

In general, used cooking oil and straight vegetable oil are thicker, heavier, and do not combust as well as regular motor vehicle fuel and are therefore likely to cause higher vehicle emissions than other types of motor vehicle fuel.

Is using vegetable oil as fuel legal?

Raw vegetable oil or recycled greases (also called waste cooking oil) that have not been processed into esters are not biodiesel, and are not registered by EPA for legal use in motor vehicles.

Was vegetable oil originally for cars?

The early 20th century also saw the start of the use of vegetable oil as a fuel in diesel engines and in heating oil burners. Rudolf Diesel designed his engine to run on vegetable oil. The idea, he hoped, would make his engines more attractive to farmers who had a source of fuel readily available.

What cars run on vegetable oil?

Firstly, not all cars can run on straight vegetable oil. Older crappier diesel engine cars are most suitable to run on cooking oil. Petrol-powered cars have a different form of combustion and are thus unsuitable, as the vegetable oils are too flammable for their engines.