Fuel System Overview

To use waste vegetable oil (WVO) in a diesel engine, you need to clean the oil, then heat it to make it flow like diesel fuel, and provide some way to switch between diesel fuel and WVO.

Cleaning The Oil: Gravity settling is popular among WVO users. It's a great way to get rid of most contaminants so that the engine filter doesn't have so much work to do. By waiting days to weeks and sucking the WVO off the top of the settling container, only minor contaminants remain to be picked up in the engine filter.

But I wanted to be able to drive non-stop, without waiting days to weeks to get rid of contaminants. So I use two cleanable filters to clean the oil as I put it into my tanks. See my filling system for more details.

Heating The Oil: When WVO is heated to about 80° Celcius (180°F), it's consistency is similar to that of cold diesel fuel. In practice, the engine starts on diesel fuel, run until hot, then a valve switches the engine to WVO. A few minutes before stopping, the valve is switched back so that the engine can start easily on diesel fuel.

Many people get away with engine heat only, by using techniques like embedding the fuel line in an engine coolant line (hose-in-hose, or HIH) or by thermally coupling fuel and coolant lines (hose-on-hose, or HOH). The former is subject to leaks and the latter needs to use special heat conducting tubing, insulated in a bundle.

In my situation, I couldn't easily use either technique exclusively, since I had a three tank design, which complicated such closely-coupled plumbing. So I use a combination of heated tanks, HOH, heated filter, and an electric heater.

Selecting The Fuel: Because I want to travel non-stop, I use two tanks and a somewhat complicated scheme by which one tank can be supplying the engine with WVO while the other tank is circulating through a filter. Two Pollak motorized six-port electric valves do the job. A third Pollak valve selects between diesel fuel for starting and stopping, or WVO from one of the two tanks. A fourth Pollak valve selects between continuous filtering of one tank, or of filling from an external hose.

Try the links at the top to get more information on various subsystems that allow Veggie Van Gogh to run on WVO, or you can step through all the pages using the "Prev | Next" links at the bottom of each page.