With diesel gas prices skyrocketing these days more and more people are turning to alternative fuels like biodiesel and waste vegetable oil WVO. You can buy a vegetable oil conversion for diesel engines that will allow you to run in any proportion diesel, biodiesel, straight vegetable oil SVO, or WVO. Some conversions are single tank like Lovecraft conversions, while other use a dual tank system that you can switch between like Veg Rev conversions. The purpose of conversions are to heat the fuel and to filter it.
It can be competitive out there in terms of collecting used fryer oil, but building relationships with restaurants can get you a dedicated supply. Choosing the right restaurant is also important because one that changes oil on a schedule will have much cleaner oil than one that changes oil out of necessity. Restaurants used to pay to have the oil removed, then it became a free service, and now some companies pay to remove the used oil because of demand. Used oil can be made into biodiesel, soap, and straight up fuel. Some restaurants will pour the used oil back into the containers they came in called cubies for collection, while others will fill a 55 gallon drum which you then pump out into 5 gallons heavy duty containers called carboys.
Managing veggie oil is a dirty messy job but can be well worth it if you have the space and time. When building a fueling station there are many things to consider such as how much space you have, how many gallons of oil you will be managing, what your budget is, and how much time you have to dedicate to this. Managing oil is comprised of two things, removing sediment and water. Oil and water don't mix afterall and can be harmful if put into a gas tank. If oil is not filtered properly sediment can "coke up" or clog the injectors, and replacing the injector pump can be costly.
A good low budget system can be comprised of a barrel, filters, and a pump. I get my polyester sock filters from dudadiesel, a biodiesel supply store with everything you need for veggie oil and biodiesel. The smaller the micron the finer the filter. Generally, one can start with coarse filtering at about 100 microns. 
With the sock filters I hang a few over a broom stick over a drum.
I use 2 drums for filtering. One is for coarse filtering at 100 microns. The other is for fine filtering down to 1 micron. Most people filter down to 5 microns. Another type of filter is a drum filter. I have also used this type of filter for coarse filtering. Some are also washable.
Pumping from barrel to barrel can be done with a manual pump or electric. I am using a hand crank transfer pump. It pumps 10 gallons per minute.
You can also use an electric pump, either 110volt or 12volt. I have used a tuthill1604 7gpm (gallon per minute) 12 volt pump with a car battery. It comes with a plastic gas nozzle and hose. Expect long back orders.
Some people use an inline fuel filter and water separator , while others use gravity and time to allow the natural separation in the container. Time also helps the sediment to settle at the bottom of a container. The rule of thumb is- never use the bottom of the barrel! Water appears white and milky while sediment can be silty or with larger particles. In a 55 gallon drum it's best not to use the oil on the bottom 8 inches just in case of settling (even after filtering.)
A centrifuge spins all of the particles and water out of filter vegetable oil before it is used as fuel. At around $1000. it is the most expensive and the most effective.
I use a four barrel system with sock filters and a hand crank pump. A coarse filter and settling barrel, a fine filtering barrel, and two holding tanks. I have used inline fuel filters as well as the gravity method. When I used the 12 volt pump, I trickled charged the battery with a solar panel. At home I filter 2 times, and then my conversion filters it another 3 times, 1 of them being an inline filter for water separation as well as sediment. Plus there's the strainer in the gas tank. My 1979 Mercedes wagon has run off 100% WVO for over 60,000 miles now! There are classes held around the Bay Area on how to make biodiesel. However, if you want to go "all in" and run 100% veggie oil then this blog's for you.
