Running a Car on Cooking Oil

OK, this is the next crazy idea. I’ve done this before with a renault clio, but unfortunately I had to scrap it shortly after, so I’m giving it another go with this car, (a renault laguna 1.9 dCi turbo diesel).

So far as I can see, there are relatively few drawbacks to using vegetable oil, the main one to worry about though, is that it’s thicker than diesel. Naturally, this puts extra strain on the fuel and injector pumps, and can possibly lead to clogging of filters, injectors and stuff.

In order to get round this, people who run their car 100% on this stuff, generally have a “conversion” done which involves fitting 2 fuel tanks and some heating equipment plumbed in to the fuel line, as the heat makes the oil thinner. There is also a US company that sells another solution, which is some sort of solvent you can mix in with the oil which does this for you, and allegedly saves you having to fork out several thousand quid to have your car converted.

Not sure about the US company, as they are called “Diesel Secret Energy” which smells of snake oil, never mind veggie oil. I may buy some of their additive, put it in some oil in the kitchen, leave it for a week and see what it does first…

With the conversion, the 2 tanks are for diesel and veg oil, the theory being you start and warm the engine up on diesel, then switch to veg oil, and with everything already being hot this should be fine, then you switch back again, a few miles before you get home to clear everything out again before it gets cold. Various estimates, depending on your fuel consumption etc. state figures of around 25,000 miles before you recoup your money, and to me that sounds like a lot of mileage. I do 20,000 a year and that’s a good 35% more than average, so it doesn’t seem worth forking out for to me.

On the continent I am led to believe that many older cars are already capable of running SVO (straight vegetable oil) with barely any modification whatsoever, it’s the more modern direct injection engines that are the problem. The finer tolerances and multiple injections per stroke and so on and so forth probably don’t give much margin for what fuel to use. I don’t know how much truth there is in that, although the handbook in my car points out there is actually a fuel heater fitted to some models, and sure enough, there’s one under my bonnet!

But why am I doing all this?

Well, it’s basically about the extortionate cost of fuel. I live in the country so I don’t have that much choice when it comes to public transport, and the fuel is more expensive than the city too. Currently, brand new unused cooking oil is £1/litre, a saving of almost 50p, and “used” I’m sure could be had for free from one of my local chippies, although that would need filtering and treating for water before use.

And what about the law? If the cost of diesel is more than 65% tax (it really is, look it up!), then surely tax is also due on veggie oil? Well, yes and no. If you use less than 2,500 litres per year, or 550 gallons in old money, then there’s no tax to pay! See the relevant page of the HMRC’s site here.

Here’s the outake:

4.2 When is excise duty payable on biofuels?

4.2.1 Exempt producers/users

If you have produced or used less than 2,500 litres of:

  • any biofuel, or
  • any other fuel substitute or additive

within the last 12 months, and/or expect to produce or use less than 2,500 litres in the next 12 months, you are an exempt producer and do not need to register with us and account for duty. However, there are simple record keeping requirements, which are described in paragraph 4.9.1.

Currently, the vehicle does 50 mpg, which is pretty good for a 12 year old car, so 550 gallons is going to take me pretty far: 550 x 50 =  27,500 miles. However, I have decided not to go 100% straight vegetable oil just yet (if I ever do), and have decided to use 1/3 veg oil to 2/3 diesel for now and see how I get on – I’ll keep you posted.


9th May 2012

Well it seems to have worked quite nicely, apart from the oily mess I left down the side of the car whilst filling it. Still, it’s not going to corrode the paint work is it?

Here’s the update on how I got on – https://inthemetal.wordpress.com/2012/05/09/veg-oil-update/

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This entry was published on May 4, 2012 at 4:00 pm. It’s filed under Fuel Efficiency, Uncategorized and tagged , , , . Bookmark the permalink. Follow any comments here with the RSS feed for this post.

2 thoughts on “Running a Car on Cooking Oil

  1. Pingback: Veg Oil Update « In The Metal

  2. Pingback: InTheMetal – Veg Oil Update

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