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Veggie Power

Converting a Diesel to Run on Vegetable Oil

Photography by Steve Temple

It really sounds too good to be true, running a diesel on used vegetable oil. Not to be confused with biodiesel fuel blends, which actually have only a small percentage of vegetable oil, we're talking about burning straight veggie oil in your engine instead of diesel, which a growing number of diesel owners are already doing. Here's the basic approach: First, you just siphon some cooking oil from a deep-fat fryer at your local restaurant, filter out any debris, and pour it into a secondary tank in your vehicle. Next, after starting up your vehicle on diesel fuel and getting the engine up to operating temperature, and also warming the veggie oil with a heat exchanger in the tank, you flip a switch that transfers over to the vegetable oil system.

Then, you simply drive down the road free of charge. That's right: zip, nada, nothing-no price gouging at the fuel pump. Restaurant owners are thrilled to see you empty their barrels, since they otherwise have to pay to have it hauled away. Or you can run on unused, food-grade oil, either fresh or rancid, which in bulk form actually costs less than diesel at the pump and requires no filtration. Not only that, by running on used vegetable oil, you're putting a waste product to good use, since a gazillion gallons or so need to be disposed of every year. Moreover, you'd be doing your part to reduce our country's dependence on foreign sources of petroleum. As for performance, your engine actually runs cleaner and quieter on veggie oil, reducing harmful pollutants, with no loss of acceleration or mileage.

So, what's not to like? Good question, one that we had to answer. That meant doing a bit of digging and getting our hands greasy. A number of companies offer vegetable-oil fuel systems-check Google for grease conversions. While similar in concept, they differ in design, and as with any new technology, it's a caveat emptor situation. So, do your homework before you start filling up buckets in your garage from your local Taco Bell, and stay tuned to Diesel Power for future features on this subject.

For this first article, we focused on one firm in particular, Veg Powered Systems, based in Ojai, California. We chose to start with this one partly because its owner Joel Woolf is a diesel mechanic with more than 20 years of experience, so we figured he knows his way around an oil-burner. Also, we were able to drive a couple of his converted vehicles (a Dodge Ram and a Mercedes sedan), and met a customer who has driven extensively with a Veg Power system on his Duramax-powered Chevy C4500 Kodiak truck.Looking at the concept in general, it's entirely plausible to run a diesel on veggie oil. After all, Rudolph Diesel originally designed his invention to run on peanut oil. The main problem is that vegetable oil is much more viscous than conventional diesel fuel, which means that before attempting to spray vegetable oil through your engine's injectors, it must be heated (thinned) in order to be properly atomized. In addition, the engine should be up to operating temperature before running on vegetable oil.

If both of these conditions aren't met, the vegetable oil won't burn properly, forming deposits on the injectors and in the cylinder head, leading to poor performance, higher emissions, and reduced engine life. To overcome these problems, the approach is to create a heated auxiliary fuel system that is activated once the proper operating temperature has been achieved.

In Woolf's Veg Powered Systems, the vegetable oil never enters the stock diesel fuel filter and is never pumped by the stock electric fuel pump. For a price of less than $2,000, the system's components consist of separate pumps, filters, fuel gauge, switch, solenoid, valves, fuel line, and an insulated 50-gallon tank to hold the vegetable oil. Mounted inside the tank is a heat exchanger made from coils of copper tubing adjacent to or surrounding a perforated pick-up tube for the vegetable fuel-oil line. Hot fluid from the engine's coolant system runs through the tubing to bring the vegetable oil up to temperature, usually in just a few minutes. Woolf points to the engine's factory water temperature gauge as a guide as to when to switch over to vegetable oil. The magic number here is 160 degrees F-anything less and you're asking for trouble.

While driving Woolf's vehicles, we checked out the changeover to veggie oil firsthand, and the transition is smooth and seamless. Simply flip a switch on the dash, and in a minute or so, the performance is noticeably quieter, while the acceleration feels virtually identical. In addition, the soot and stink are markedly reduced. Can you imagine a diesel that actually smells good and runs better? And on free fuel? Of course, as with all new-fangled inventions, there are a few complications and downsides. One of them involves shutting off the vegetable oil and purging the fuel system with conventional diesel fuel. This step is required before turning off the engine for any length of time, in order to prevent cooled vegetable oil from clogging the fuel system-although, probably not necessary for short stops of an hour or so, depending on the ambient air temperature.

The length of time to purge the system is not precise, but you can hear the change in engine sound. Woolf advises switching back to diesel for a minimum of 3 to 5 minutes (or a mile or two from your destination). The solenoids and valves that handle the changeover are similar to what you'd have with an auxiliary tank containing conventional diesel fuel, so this technology is nothing new. Another potential downside is the hassle of filtering used vegetable oil by hand, but Woolf has a solution for that. In the early days of the veggie oil movement, recycled oil was laboriously poured by hand through a large, sock-shaped filter, which can take hours and leave a mess of dirty buckets of used oil. Instead, Woolf has invented an onboard filtration system that costs about $500. It has two or more filters that step from 14 down to 4 microns, essential for the new common-rail fuel systems with higher injection pressures.

To demonstrate the system, Woolf pulled up behind a local restaurant, after calling the chef for permission beforehand, and stuck one end of the hose into a barrel at the back door. Woolf turned on a battery-powered electric pump that sucked up the fuel, and he fed it through the filters and into the auxiliary tank. Later on, he plans to add an automatic reel under the bed to retract and store the hose. The whole process took no longer than filling up at a regular fuel station, with one big difference-he didn't have to pay for the oil. In fact, the owner of the restaurant actually asked Woolf to return within the next week to pick up some more used oil.

The size of the tank on your vehicle can vary, but a typical full-width toolbox found in the bed of a pickup can hold a 50- to 100-gallon tank (mileage is roughly the same, depending on the type of fuel system). As most Diesel Power readers already know, diesels are great for hauling heavy loads, so you'd hardly know all that veggie oil was in the bed. Passenger cars are a bit more of a challenge, since there's less storage space for an extra tank. We also wonder about having a heated tank of oil next to a bag of groceries. Just keep the ice cream and other frozen foods in separate area, and they'll probably be OK.

A certain amount of mechanical understanding, if not experience working with diesels, is helpful. However, one customer we met, Paul Powers, who runs a Chevy C4500 Kodiak outfitted with a utility bed and camper top, admits to minimal experience working on diesels. He's thrilled with his Veg Powered Systems, and he runs it up and down the state of California. He reports no difficulty towing a trailer loaded with a steam cleaner which he uses to maintain supermarket parking lots all around the state. He also notes with pride that he recently saved more than $1,500 on diesel fuel on a trip from Southern California to Canada and back, in which he ran on vegetable fuel for 95 percent of the time. "It's a great feeling to get in a vehicle and go, knowing you're burning vegetable oil," he enthuses.

Powers prefers getting his oil from Asian restaurants because he feels it's better than fast-food oil. "The number one thing is to use really clean, grade-A oil," Powers advises. "Inspect it to make it sure it's not hydrogenated. You can run hydrogenated oil, but you'll run into more problems clogging filters and fuel injectors." Powers has a set route of restaurants where he collects oil and uses a manual, hand-crank pump to pull as much as 14 gallons per minute. He also sells excess oil he filters to fellow veggie oil enthusiasts for $1.50 per gallon. He claims his custom-fabricated filtering setup can handle as much as 500 gallons day.

The only hurdle he's encountered was some thick oil in a filter during cold weather, but he recently installed a 300-watt fish tank heater in his tank and hasn't had a problem since. He points out that an engine block heater might work equally as well. Powers has been running on veggie oil for about six months, and since he drives more than 30,000 miles year, he figures he saves about $1,000 per month. Speaking of money, let's say you drive 15,000 miles in a year on veggie oil and burn an average of 15 mpg. That means you've consumed 1,000 gallons. At $3 or more per gallon for No. 2 diesel, you'll save at least $3,000, not counting the cost of replacing filters every 3,000 miles. So, theoretically, a $2,000 unit from Veg Powered Systems can pay for itself in a matter of months.

How about the long-term effects of using straight vegetable oil in a diesel engine? Few, if any, formal studies have been done on the subject-and likely not by any big petroleum companies-but there are a lot of articles on the chemistry of using vegetable oil as a fuel. In general, they point out that some vegetable oils are better than others: Palm and hemp oils are preferred; linseed or hydrogenated oils are not recommended. They also note that certain diesel engines are more suitable than others, such as older, '80s-era Mercedes, in particular, work well. Also, some injection pumps work better than others. Whatever the type of engine or fuel system on your vehicle, ensuring the quality and cleanliness of the vegetable oil is obviously a key factor in the reliability and performance of a conversion system.

Even with those cautions, given the skyrocketing cost of diesel fuel, having the option of running on free vegetable oil still has considerable appeal. We'd be interested to hear from any readers who are currently running vegetable oil in their diesels and what sort of experiences they've had. We'll let you know what we find out.

SOURCES
Veg Powered Systems
www.vegpoweredsystems.com
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