We like to answer reader questions with our Greenlings series whenever possible, and thought that Timothy H. had a good topic. He sent in the following question/suggestion about straight vegetable oil (SVO):
I have seen several articles dealing specifically with SVO, but not as it concerns the economic viability compared to petro-diesel. I mean there are articles out there, but I'm interested in knowing why I should/should not use SVO in my car, what benefits I have to look forward to, what problems people have had from using it, etc. Is it really as simple as heading to a Chinese restaurant and heckling $5 for a 50 gallon jug of WVO, then filtering the oil before it goes in the tank? If it isn't that easy, what is making it hard? Why are so few people making the jump if the conversion can pay itself off in two to three years?
We've got the answers for him – and everyone else who's interested – after the jump.

[Image: ROBYN BECK/AFP/Getty Images]



To start with, we'll refer readers who are new to the homemade biofuel scene to this previous Greenlings post on the difference between biodiesel and SVO. If you're clear on what SVO is, then we can continue.

Why use SVO?

There are many benefits to using SVO. The big ones are that you can collect your own fuel (take that, foreign oil interests!) and that it can be a tremendously cheap or even "free" (with time investment) fuel. Most SVO users make deals with local restaurants that deep fry a lot of food and need to get rid of their waste grease somehow to pick up this used oil. In the past, all restaurants could do was pay a waste company to come and haul the dark yellow liquid away. Now, with people willing to schlepp the used oil away for free, the economics of SVO have changed. In some places, it's still available to pick up for free. In others, it's kind of expensive. One recent posting on Craigslist was offering filtered SVO for $1.50 a gallon. Sure, that's cheaper than both petroleum diesel and biodiesel these days, but is it cheap enough to get people to make the switch? Not always.

SVO's environmental benefits are amazing, too. Instead of petroleum fuel, you can drive using a truly recycled product. The oil was already used once to make french fries or bloomin' onions, and now you can use it to get home from the restaurant. Emissions are lower than standard diesel, too.

Photo by 300td.org. Licensed under Creative Commons license 2.0.

How to use SVO?

While some people will tell you it's OK to use straight veggie oil in any diesel engine with no need for modifications, we're not going to. We've heard too many stories about problems with putting these sorts of fuels into engines that weren't designed for them to suggest any such thing. Still, one shouldn't be afraid of trying SVO. The problem is that to use SVO, the best first step is to convert your fuel system in your diesel car to accept the non-petroleum fuel. It's also better to use SVO in an older diesel car – 1970s and 1980s Mercedes-Benz vehicles are popular choices. We're sure some people reading this are handy enough to install a second tank and the associated fuel line components, but if you're not one of them, there are also many kits and mechanics available who would be happy to do the work for you (starting at around $2,000). This initial cost is one thing that holds people back from trying SVO.

Once you have the system installed, though, it is possible to "heckle $5 for a 50 gallon jug of WVO" (waste vegetable oil, which is the same thing as SVO). From there, the oil needs to be filtered and dewatered, both of which are easy to do at home but take time. Frybrid recommends filtering the oil to at least two microns and to remove any water in the oil down to 500ppm. Again, another step that can make using SVO daunting to the average driver.

Once in the car's fuel tank, it's quite simple to use SVO. You start the car on diesel and let the fuel system heat up, then switch which tank the fuel comes from and off you go. Easy as french fries.

So, what's the problem?

Even with all of these benefits, using SVO is not as simple as some proponents make it seem. Journey To Forever is a great resource for learning about SVO (especially in comparison to biodiesel) and lists a few of the problems with SVO usage, including how vegetable oil crystallizes in cold weather. Their short list of things to consider:
  • Some diesel engines are more suitable than others.
  • Some vegetable oils are better than others.
  • Some injection pumps work better than others.
  • Some SVO kits are better than others.
  • Some computerised fuel systems don't like vegetable oil at all.
  • There are doubts about using waste vegetable oil.
  • There are doubts about using straight vegetable oil in DI (Direct Injection) diesels.
The DOE adds (PDF) that, "The long-term effect of using SVO in modern diesel engines that are equipped with catalytic converters or filter traps is also a matter of concern." These are just some of the potential problems – all of which are solvable – that prevent more people from getting into SVO.

What about the economics? Isn't free fuel too tempting to pass up?

Part of what makes answering Timothy's economic viability question so difficult is that the "correct" answer varies depending on where you live. If you live in a densely populated area with a lot of restaurants and not a lot of competition for the waste grease, then it can be quite easy to collect many gallons in a short amount of time. But, if you live in a rural area and it takes 45 minutes or more to hit up enough establishments to fill your tank, then it might not be worth your time. Filling up at the diesel pump might be more worth it when it one considers time and investment of materials like barrels and filters. Also, if there are a lot of other grease collectors in your areas who want the waste oil for their own SVO vehicles or to make into biodiesel, then it isn't as easy to collect enough SVO simply. Of course, the price of diesel fuel plays a role, too, and the calculations change with the price at the pump. With higher fuel prices and more eduction to make people feel comfortable getting a bit dirty collecting their own fuel, SVO adoption rates will surely rise.