I often get asked if there are any drawbacks associated with running a diesel engine on vegetable oil, and of course there are.
Below I've listed these, in no particular order, if only to prove that I'm being objective. The other pages on this site may make veg oil motoring appear somewhat idyllic, so I thought I should try and balance this out by pointing out the worst drawbacks I can think of. This way, at least, you'll be better prepared should you decide to take the plunge...
It costs money to have your engine professionally converted to run on vegetable oil. It's not cheap either... think in the region of several hundred pounds or more. I can't give an exact figure because I don't fit these things for a living, so contact professional fitters who will give you free advice.
Similarly if you're going to collect and filter waste vegetable oil, there's set up costs associated there. You can control this budget more carefully, as it's a DIY thing, but a couple of hundred pound may still be required - more if you want fancy filters, pumps, etc.
On a positive note, once these initial set up costs have been shouldered, you should be able to recoup your costs and much more besides when you actually begin driving on veg oil.
Whether you buy your veg oil from the shops, or whether you recycle WVO, you've still got to get the oil into the tank. The chances are you're going to have to haul large containers holding 15 or 20 litre's of veg oil around, lifting and pouring with care. These containers are surprisingly heavy. I'm a fairly strong guy but I've been known to struggle doing this. Don't underestimate the difficulty.
Sooner or later you're going to spill some veg oil. I spilled a couple of litre's on my block-paved driveway. I wasn't happy. Fortunately I remembered an old trick - pour cat-litter on it and leave it for a few days (take a look at my cleaning-up section). This trick worked, soaking up most of the oil, but it did leave an oil stain. However, as you've heard me mention elsewhere, vegetable oil is biodegradable and sure enough after a few weeks the stain disappeared.
However it is a messy substance. When it's poured it seems to hug the outside of the containers, running down the sides on to your hands, dripping on the floor, making an oily puddle when you place the container down. You always need to think in terms of drop-cloths, paper-towels, etc.
If you filter WVO then you'll really discover how smelly, sticky and messy veg oil can be. Your clothes will get covered in it and everywhere will become cluttered with containers holding various stages of oil and sludge.
Unless you're extremely well organised or have a fantastic memory, the time could well come when you forget to switch off the veg oil a few minutes before your journeys end. If the engine cools and there's veg oil inside instead of diesel, you'll have a nightmare of a time starting your car. I've dedicate a whole page to this subject which I suggest you read carefully.
Obviously I'm a confirmed veg oil driver. I've been doing it for a few years now. There is great pleasure in knowing that you're doing your bit to help the environment. Also it certainly helps save a few quid as well, and that can't be sniffed at.
However, I will confess, if any local forecourt starts selling vegetable oil at the pump for half the price of diesel, I'll be a very happy man. I'll give up filtering WVO and enjoy the luxury of convenience.
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