(The couple in this article will be referred to as John and Jane to prevent their state's Department of Revenue showing up for non-payment of state taxes on road fuel usage.) 

This couple stretches their fuel dollars not by increasing the efficiency of their diesel vehicles but rather through burning an inexpensive alternative fuel, waste vegetable oil (WVO). The end product is generally called biodiesel.

They obtain the WVO from several restaurants either as free haul-away (saving the restaurants some pick up costs) or through bartering.

The WVO is filtered several times and mixed with standard diesel oil. Ratio depends more than anything else on weather. During winter they may run 80/20 diesel/WVO. During summer they may run 20/80. John estimates through the year they average about a 50/50 mix. They noted their compact diesel pickup obtains about 45 mpg on 100% diesel. Thus, they estimate they are obtaining somewhere near 90 mpg from each gallon of diesel by stretching it out with WVO.

They report no problems with starting even on cold mid-western winter mornings when they run the 80/20 mix, nor in summers when they run the 20/80 mix. They also report no noticeable difference in vehicle performance between the 80/20 and 20/80 extremes. However, John did note it took him a while to adjust from driving a full-sized pickup to a compact one.

In addition to two early 1980s diesels (compact pickup and sedan) they also run all of their diesel farm and business equipment on the mix. John noted when they are putting up hay he isn't sure which smells better, the fresh cut hay or the WVO fumes. He also noted he can tell the prior usage, such as for french fries, fish or chicken.

They essentially made no changes to their vehicles or equipment. However, the fuel filters may have to be changed more often (see below). Others have reported filter life with WVO not being out of line with the recommended fuel filter change schedule of the manufacturer.

On filtering, another party told me they do the initial straining though paint filters, then a 10 milcon filter in the line from the holding tank to vehicle's tank, plus replacing the in-line filter in the vehicle "when it seems to run a bit sluggish."

From some research strained WVO seems to be used in two ways:

• In the manner John and Jane do, just straining and mixing with diesel with the ratio varying through the year.
• For roughly $1,000 a vehicle can be converted to run on 100% WVO. Depending on the vehicle, normally this requires the installation of a small separate tank for diesel (with the original tank becoming the WVO storage tank), fuel lines and pumps, tank heater, filter and electrical system. Typically the vehicle is started on 100% diesel. Once the engine and WVO storage tank have warmed up it is manually switched to 100% WVO. Depending on weather, a couple of miles before stopping for any extended period the engine has to be switched back to 100% diesel to clean out the lines. Otherwise cool or cold weather may cause the WVO to gel, clogging the line. On one forum discussion someone who does this noted you don't overlook switching back to diesel before stopping more than a couple of times.

My understanding is there is no problem with either system in running on 100% diesel for a long trip. You may start out with a mix and then refill the tank with diesel once it runs low. When back home a switch is made back to the mix. For example, you return with a half-empty 16-gallon tank so adding eight gallons of WVO brings it to 50/50.

This is out of my area, so I am going by somewhat limited research in that fuel systems of older diesels tend to be more WVO friendly than newer ones. However, biodiesel can degrade some old fuel lines so they may have to be replaced and the fuel filter may have to be relocated to make changing it easier (see below).

If you are considering this I strongly recommend you consult in advance a diesel engine mechanic with experience in using biodiesel, particularly WVO, in your specific engine. Use of biodiesel may also void the factory warranty so check out that aspect also.

WVO will likely never be a major alternative fuel simply due to supply. From what I can tell, if you drive enough miles to justify the time and effort involved with WVO it will likely take the output of two or three sources to keep you supplied. A small town may only be able to support one biodiesel user. You may also be required to take all of what is produced, even if it exceeds your demand.

I suspect a restaurant owner may be willing to give it away for free if only one person inquires about his supply. When the second one does likely their thoughts may turn to competitive bidding for it.

I wouldn't recommend paying for extensive retrofitting or a full conversion unless you had the source of supply locked up, such as owning a restaurant yourself.

And I would stress WVO is not "free" as there are the expenses, however small, of collection, storage and straining.

You can find a good bit of information on using WVO, plus other possibilities, by doing an Internet (e.g., Google) search on biofuel or biodiesel.

One site is www.biodieselnow.com, which includes these aspects:

• Engine life. Studies have shown it reduces engine wear by as much as one half, primarily because it provides excellent lubricity. Even a 2% biodiesel/98% diesel blend will help. (Please note this implies even if you don't use biodiesel just adding some new vegetable oil to each tank can provide significant benefits. I have been told new soybean oil is available at Costco for around $3.50 per gallon.)
• Drivability. We have yet to meet anyone who doesn't notice an immediate smoothing of the engine with biodiesel. It just runs quieter, and produces less smoke.
• Biodiesel will clean your injectors and fuel lines. If you have an old diesel vehicle, there's a chance that your first few tanks of biodiesel could free up all the accumulated crud and clog your fuel filter. But this is a good thing...think of it as kicking up dust around the house when you clean. (As noted this seems to be fairly common when a vehicle which formerly ran on diesel is switched over to biodiesel. After a couple of filter changes it should go back to within the manufacturer's specification for routine changing.)
• It has a higher gel point. B100 (100% biodiesel) gets slushy a little under 32°F. But B20 (20% biodiesel, 80% regular diesel—more commonly available than B100) has a gel point of -15°F. Like regular diesel, the gel point can be lowered further with additives such as kerosene (blended into winter diesel in cold-weather areas). (I have read a report of one farmer in Wisconsin who operates their diesel farm equipment on 50/50 kerosene/biodiesel during winter.)
• Vehicles older than mid-90s might require upgrades of fuel lines (a cheap, easy upgrade), as biodiesel can eat through certain types of rubber. Almost all new vehicles should have no problem with biodiesel.

As an aside, I recall reading about one dairy farmer who simply top-dressed his cattle's dry feed with WVO.

(If you are running a vehicle on alternative fuels please let us know your experience with it. You can request your name and/or location not be cited in the submission if used.)