As the prices for petrol and diesel continue to remain high, should you consider cheaper alternative fuels like cooking oil? As with the cost of living crisis and skyrocketing fuel prices continuing to impact household budgets, it’s easy to see why drivers are seeking alternatives. For some, this means reducing the amount they drive by walking, cycling, or using public transport, while others could be considering running their car with cooking oil or making the switch to an electric car to reduce the cost of filling up.
While the concept of running a car on cooking oil isn’t a new one, the dramatic increase in the cost of fuel in recent years has reignited interest in the idea, helped by a video that went viral in 2022 that showed a driver filling his fuel tank with cooking oil. Here, we run through what you need to know to run your car on Hydrogenated Vegetable Oil (HVO), how it compares to Waste Vegetable Oil (WVO), and whether filling up with cooking oil or making biodiesel yourself is a viable alternative.
Can you use cooking oil in modern cars?
The first thing you need to know is that cooking oil is not suitable for use in petrol engines. This is due to its heavy viscosity, which makes it too thick to be ignited by a spark plug like petrol. Additionally, it can clog up the fuel pump and lines, as well as cause ignition problems by confusing the sensors that regulate the amount of fuel required to make an engine run correctly.
This means that if you drive a petrol car and you’re seeking a way to reduce the running costs, consider switching to a more economical car, an electric car, or one of the many car sharing services available.
If you drive a diesel car, though, you might be thinking ‘Right then, let’s go grab some sunflower oil.’ But hold on because it’s not quite that simple.
As we mentioned before, the heavy viscosity of cooking oil means it can clog the ultra-high pressure fuel injectors modern diesels use, and there’s still the problem of it confusing fuel metering sensors. As a result, there’s a school of thought that cooking oil is best suited for much older diesels with low-pressure injection systems and fewer electronics. But, even in those cars, cooking oil can still clog up the fuel filter and lines, causing other problems and expenses further down the line. Cooking oil also doesn’t burn as completely as diesel, so the engine won’t run as smoothly. The car will also smell vaguely of chips.
There are, however, ways of getting around the problems of using cooking oil to fuel a modern diesel car.
Modifying cooking oil for use in cars
Firstly, it is possible to modify cooking oil to run a car. But don’t go tipping the waste oil from last night’s dinner into your car’s fuel tank just yet (we’ll come onto that). As we mean the clean, unused HVO available from the supermarket.
To modify oil to run a car, you need to add regular diesel to it. This makes it thinner, reducing the rate at which the fuel system will eventually clog. The oil also burns better so the engine runs more smoothly. Modifying the oil doesn’t eliminate the problems it can cause, but it does increase the time between trips to the garage.
Converting your diesel engine to run on cooking oil
As we’ve established, fuelling your car with cooking oil presents some problems. But you can modify your car to get around them.
First thing that’s needed is another fuel tank for the oil. Having separate tanks allows you to choose whether oil or diesel is used at any moment, though the car will always start on diesel. The oil tank is heated to reduce viscosity, so it’ll flow through the fuel lines and atomise into the cylinders more efficiently.
On top of that, the engine needs new fuel injector nozzles with better filtration, specially designed glow plugs and new coolant lines. Add all that up and you’re looking at around £2,000 for a full conversion.
There are a number of cooking oil diesel conversion kits on the market to convert your car, and there are actually a few vehicles that run on HVO available to buy brand-new. But, as they’re Mercedes Unimog off-road trucks, they’re not exactly practical family transport!
Do I need clean cooking oil to fuel my car?
You can’t just tip cooking oil straight from the pan into your car’s fuel tank. It’s full of food particles and fats that will quickly clog your engine. You can filter oil by straining it through fine fabric, but that’s fiddly and messy. Besides, a single domestic kitchen is highly unlikely to generate enough WVO to fill a fuel tank.
WVO filtration is big business, though, worth almost £6 billion globally in 2019. Big-name oil suppliers like Oileco and Cator Oils buy WVO primarily from commercial kitchens and other sources which generate over 100,000 tonnes of the stuff annually in the UK alone. The WVO is filtered several times to make it clean enough to use as fuel. McDonald’s famously runs its fleet of commercial vehicles on WVO collected from its restaurants’ fryers.
Filtered WVO is generally only available to commercial vehicle fleets. It may take some time to find a supplier who’ll sell you some to run your car on, and you might have to buy in bulk. But there could be an enterprising local chip shop that filters and sells its own WVO.
What’s the difference between vegetable oil and biodiesel?
Biodiesel is essentially vegetable oil with the glycerine removed – that’s the stuff that makes oil thick and gloopy. However, there are many standards biodiesel must meet for it to be sold as such, which cooking oil doesn’t.
According to Oileco, one of the biggest WVO refiners in the UK, biodiesel burns 88% cleaner than regular diesel. Biodiesel is a good way of reducing your carbon footprint, then, but it’s not without environmental issues. Planting crops for biofuel can reduce biodiversity and divert agricultural capacity from the food chain.
Is it cheaper to use cooking oil in my car?
Until early 2022, 80% of sunflower oil sold in the UK was sourced from Ukraine. Since the country was invaded by Russia, the price of all cooking oils spiked to an all-time high.
At the time of writing, one litre of supermarket own-brand vegetable oil typically costs around £1.99. By contrast, the average cost of a litre of diesel is around £1.53. The maths aren’t in oil’s favour.
You could buy in bulk from a cash-and-carry or Amazon. You can also find WVO sellers on Facebook Marketplace and eBay, though it’ll probably need filtering which leaves a lot less oil than you started with.
Once you factor in the cost of converting your car’s engine to run on vegetable oil and any filtration equipment you need, it starts to look quite expensive. Unless you can find a friendly local chippy selling cheap, filtered WVO, it’s best to stick with the black pump.
- For more advice and how-tos, check out Parkers’ ultimate guide to car care
