For the last 600 miles, my Volkswagen Polo 1.4tdi has been running on a mixture of diesel and vegetable oil.
It's an experiment I've been wanting to run for 2 years but I'd been put off by the antiquated Inland Revenue taxation regime on fuel. That was scrapped recently so you can now put vegetable oil in your car without paying fuel duty. (Check that your car can run on biodiesel before trying this!).
I have done no modification to my 2001-built VW Polo so I was a little apprehensive for fear of damaging the engine. The car is designed to run on diesel, but the handbook states that it can run on up to 50% RME (Rapeseed-Methyl-Esther) mix, so I should be safe. Some diesel engines require modification because vegetable oil is more viscous and puts more strain on the fuel pump. It can also be harder to start the engine in winter.
To minimise the risk, I used a 1:4 mixture in my first tank. My mix is:
- 80% diesel
- 20% vegetable oil
The price of diesel recently rose above £1.00 per litre. Vegetable oil costs about 55p per litre in the supermarket. So, by using a 25% mix, I saved about £4.05 on a tank of fuel. On my next tank, I will use a 50% biodiesel mix, and will save over £10 per tank.
There was no noticeable change in the average MPG (miles per gallon) – I recorded 68mpg which is what I achieve with standard diesel.
Biodiesel is, arguably, better for the environment than diesel. It comes from a renewable source and the CO2 emissions are equal to the sequestrated amount when the vegetable grows, so it is carbon neutral. However, some people believe that it is contributing to the destruction of rainforest as Malaysia, Indonesia and other developing countries cut down their rainforests to plant palm oil, which can also be used as a biofuel.
Seeing as I am burning sunflower or rape seed oil, I don't think I am having a direct effect on rainforests. But if I wanted to run the ultimate biodiesel car, I would copy my mate Adam and collect used vegetable oil from the local fish and chip shop, run it through a filter then stick it in my car. It's free and it's an otherwise waste product. Everyone's a winner!
If you want to investigate biodiesel, there are lots of useful websites. I recommend this one to start with.