Introduction
To use Biodiesel in a diesel engine, simply pour it in the fuel tank and use the engine as normal.
Yeah, it's THAT simple. No modifications, no second fuel tanks, no heat exchangers, just pour it in and go.

Biodiesel can also be blended with petrodiesel in any ratio. Pure Biodiesel is labelled B100 (the number representing the percentage of Biodiesel), when it's blended, it's labelled with the percent of Biodiesel after the B. For example, B90 is 90% Biodiesel, 10% some other fuel (typically petrodiesel).

Fuel Lines
On diesel engines made before 1993, the fuel lines were typically made from rubber (usually nitrile rubber). Biodiesel's solvent properties tend to break these down over time. It is recommended that when using Biodiesel in pre-1993 diesel engines that the fuel lines be monitored for breakdown and possibly replaced, especially when using blends of 30% Biodiesel or greater. Viton fuel lines or other synthetic (non-rubber) fuel lines can be used as replacements. Diesel engine vehicles made after 1993 usually are 100% compatible with Biodiesel. If in doubt, check with the manufacturer.

Fuel Filters
When first using Biodiesel it is recommended to replace the fuel filter on your engine. Because of the solvent properties in Biodiesel, it may cause the release of accumulated deposits inside the fuel tank and fuel lines from years of petrodiesel use. These deposits can flow down the fuel line and may plug the fuel filter. Luckily, most of the time the filter's don't plug all at once, but slowly, causing slight hesitations in engine acceleration, missing (cylinder's not all firing), or other sluggish behavior.

A good rule of thumb to follow is to replace the fuel filter before beginning to use biodiesel and then replace it again after a few thousand miles of Biodiesel use, especially if using percentages of Biodiesel of 30% or greater. Think of it this way, Biodiesel is not only good for the environment, but it actually acts as a fuel system cleaner, cleaning the injectors, fuel pump, fuel tank, and fuel lines. In fact, it's solvent properties are so widely known that many fuel additive manufacturer's use it as an ingredient in several of their additive products.

Emmissions
One of the benefits of using Biodiesel in a diesel engine is that it can help to reduce the amount of tailpipe emmissions. In fact, studies have shown that there is a substantial reduction in the amount of carbon monoxide, unburned hydrocarbons, carbon dioxide and particulate matter over emmissions that Petrodiesel emits. It also has a nice effect of changing the smell of the exhast. Most people say that it tends to smell like french fries. Kind of a nice swap over the petrodiesel smell--that is unless you like that smell.

Biodiesel emmision benefits begin with the use of a relatively low blend of biodiesel. Studies have shown that a noticable difference has been measured with even a 20% mix of Biodiesel in Petrodiesel (B20). Continued use of Biodiesel overtime will also help the engine to run better due to the fuel system becoming cleaner.

Engine Warranties
Several diesel engine manufacturer's will warrant the use of Biodiesel that is commercially made up to B20 and some even beyond that. Check with the manufacturer for specific details.

Engine Performance
Biodiesel has been shown to produce similar performance when compared to Petrodiesel. One noticable difference, fairly quickly after using it, is that the noise emmision of the engine goes down. Sometimes drastically, depending on the engine it's used in. This is due to Biodiesel having a higher lubricity than Petrodiesel. Think of it like this. It's "slipperier" than Petrodiesel. There's lots of chemical stuff that can explain it, but for the average user, the noticable difference is a quieter engine, easier starts, and less vibration. The effect increases as the percentage of Biodiesel used increases per gallon of fuel.

There has been documented evidence that shows there to be a slight decrease in power, somewhere between 5% to 10%. This is due to several factors, but essentially, it has to do with the BTU equivalent of Biodiesel when compared to Petrodiesel. Most users don't notice this small of a decrease in power while gaining all of the benefits. Individual results may vary.

Cold Weather Use
Here in Utah we run into a problem. It get's nice and cold in the winter time. Diesel fuel in Utah is winterized each winter to prevent one big problem; gelling fuel. Biodiesel has the same issue, it has the potential to gel. In fact, Biodiesel has a higher gel point than Diesel fuel. If you plan on using Biodiesel in the winter in Utah, plan on "winterizing" it. To do so, most people just blend with petrodiesel at about a 50% mix (B50). Using a 50% mix should allow you to run your diesel in the winter without any problems. Visit this link for some great advice on how to winterize your biodiesel.

National Biodiesel Board
The National Biodiesel Board (NBB) offers a wealth of information on using Biodiesel.
Click Here for some great Fuel Facts

Real World Experiences With Biodiesel
Curious about how others have faired? Click Here to read real world experiences from people about Biodiesel and it's effects on their diesel vehicles.

A great article from the Winchester Star from Virginia
Click here to read the article

Popular Diesel Manufacturers Forums
The Diesel Place GM/Chevy Duramax Diesel Forum
The Diesel Stop Ford Powerstroke Forum - Direct Link To Alternative Fuels Sections
Ford Super Duty Diesel Forum Direct Link To Alternative Fuels Section as well.
Cummins Forum Dodge Cummins - Direct Link To Alternative Fuels Sections

Diesel Power Magazine
Diesel Power did a great analysis of running Biodiesel in diesels called Living With Biodiesel.

MSN Autos
This is a great article on "Biodiesel Becoming Mainstream" gives an interesting insight into using Biodiesel and diesel engines.

University Study of Biodiesel Anti-Gel Additives
The University of Idaho conducted a study of some of the leading Biodiesel Anti-Gel additives on the market. Click here to view the results