Vegetable Oil - A Fuel For Your Car?

By: Jamie Weaver

I was filtering vegetable oil for my truck the other day and decided it would be a good topic to write about.  There are a lot of misconceptions about running a vehicle on vegetable oil and I wanted to clear some of them up.  I converted my 1984 GMC Suburban to run on Waste Vegetable Oil 8 years ago and it hasn't given me any trouble…well the veg oil system hasn't…the truck itself is pretty old and has given me it's share of headaches.  

Waste Vegetable Oil (WVO) means that the oil is used, generally by restaurants, and would otherwise be thrown away.  This is an important distinction as some biodiesel companies are using vegetable oil produced specifically for biofuels.  This poses potential issues as growing crops for these fuels uses land, water, nutrients and other resources that could otherwise be used for growing food.  The growing popularity of these fuels could lead to the decimation of large tracts of land, not to mention all the fossil fuels used in the production of the oil in the first place.

Another word for the fuel I am using is Straight Vegetable Oil (SVO) which means what it sounds like, pure vegetable oil.  This is opposed to biodiesel which is a mixture of vegetable oil and very specific ratios of lye and methanol.  Adding these chemicals to vegetable oil makes it possible for any standard diesel vehicle to run on this fuel, where with SVO the vehicle itself must be converted.  I prefer converting the vehicle over the fuel as I don’t have any interest in dealing with corrosive chemicals on a regular basis.  Also, converting the vehicle is a onetime deal, while converting the fuel must be done every time you get a new batch.

Only diesel vehicles can be run on vegetable oil.  There are other creative things that can be done with standard gas cars such as making your own ethanol from plant matter such as corn, beets or potatoes (much like distilling alcohol) and converting your vehicle to run on 85% ethanol.  But, unless you can find ways to use a waste product, this again creates competition with food production.

Diesel vehicles are actually very well equipped to run on vegetable oil as is. The first diesel engines, though created to run on coal dust, were soon found to be able to run on peanut oil without trouble.  Although present day diesel engines are more suited to run on petroleum based diesel fuel, functionally the main difference from vegetable oil is the viscosity.  Vegetable oil is much thicker than diesel and must be thinned out before it can be vaporized and combusted in a standard diesel engine.  The most common way to do this in a SVO converted vehicle is to heat up the oil until it reaches about 175 degrees Fahrenheit.  This is generally done by running the coolant lines along the vegetable oil fuel lines and through the inside of the vegetable oil tank.  When the vehicle is running the coolant heats up and in turns heats the oil in the tank and fuel lines.  In order for this to work the vehicle must be started on regular diesel fuel then be switched over to veg oil once warmed up.  Since diesel combusts at 410 degrees Fahrenheit, this doesn’t take long.  I generally wait until I’ve driven about a mile and a half before switching over to vegetable oil.  Likewise I switch back to diesel a mile and a half before I get where I’m going.  This purges the lines of vegetable oil and makes sure there is diesel in the engine when I go to start again. 

There are really only a few components that need to be altered or added to your vehicle for this system to work. You need to add a second tank to your vehicle, fuel selector valves, and some toggle switches so you can switch from one tank to the other.  You also need some additional fuel line, a bunch of coolant line to splice into your existing coolant system and an additional fuel filter for your vegetable oil.  But that’s about it.  To get the details and learn the full process you will have to come to our class on Vegetable Oil Conversions (to be announced)

But let’s talk about filtering the oil.  As I stated before Waste Vegetable Oil is the used oil from the deep fryer at restaurants.  Restaurants can only use the same oil so long before they have to change it out.   Prior to the increase in biodiesel and veg oil vehicles, restaurants generally had to pay to get rid of their used oil and were more than happy to have you take it off their hands.  Now many restaurants have contracts with biodiesel companies that pay to take their oil from them.  This makes it much harder to find oil for personal use.  But not all restaurants have been swooped up and persistence pays off.

When you finally get some oil it is often rancid and mixed with burnt French fries and chicken fat.  Don’t worry, this oil will still work fine, however this is not something you put directly in your tank.  It would be great if we could just pull up to a McDonalds every time we were running low on fuel and fill up right there.  But that is generally not the case.  Although I have heard of a quick filtration method using a centrifuge filter that essentially spins the oil and splats all the unwanted solids against the outside, allowing the person to filter oil as they collect it and put it directly in their tank.  Most people however use a much slower process. 

My first step in filtering oil is to let it settle for a week or so.  This allows the fatty solids to settle to the bottom so you can pour the clear oil off the top.  Skipping this step will clog any filter in seconds.  I then pour the oil through a 100 micron screen filter into a 55 gallon drum.  This filters out any old french fries or debris that might be floating in your oil and any fatty gunk that made it through the pouring process.  

The next stage involves running the oil through 2 more filters, a 10 micron filter and a 1 micron filter.  The standard fuel filter in your vehicle filters to about 10 microns, so doing it to 1 micron is a little bit overkill, but doing so means I won’t have to worry about the filter in my truck clogging up mid drive and it is a lot easier on my engine and the injector pump in the long run.  For this process I use 2 standard in-line water filters that I hooked up to the bottom of my drum.  Notice that I attached the pipe a few inches from the bottom.  I try not to pour any new oil into the drum for at least a few days before I start pumping the oil through these filters.  Leaving a little space at the bottom of the drum gives a place for any leftover fatty solids to settle so they don’t clog up the filters. 

To pump the oil through the filters I use a 12V water pump that was made for use in an RV.  I hook it up to my truck battery and attach it to the end of my filters.  It works pretty well and I don’t need an on-grid power source to use it.  Doing the filtering sequentially like this, 100 microns then 10 microns then 1 micron, helps keep your filters from clogging which also keeps the rate of flow up.  It takes about a minute to fill up this 2 ½ gallon gas can, then I pour it into my tank and I’m ready to go!  If your system is set up somewhere you can drive up to you can pump the oil straight into your tank.  The veg oil tank in my truck holds about 30 gallons, so I can get about 2 fill ups from one full drum of oil.  It usually takes me long enough to go through that much oil that the next batch has adequately settled and is ready to filter.

I Hope this has been a useful summary and has peaked your interest a bit about alternative fuel sources.  Thanks for checking us out!

 My trusty luck dragon - Falcor

My trusty luck dragon - Falcor

 Fuel Selector Valve

Fuel Selector Valve

 Toggle switches

Toggle switches

 vegetable oil filter wrapped in coolant lines

vegetable oil filter wrapped in coolant lines

 100 micron screen filter

100 micron screen filter

 Filter System

Filter System