Using biodiesel that is made commercially is typically no different than using petrodiesel, but it can be a good idea to contact the manufacturer of a vehicle before switching over. Some manufacturers may have concerns, though in many cases the only circumstance to watch out for is plugged fuel filters. Homemade biodiesel can be another matter, since each batch may be of a slightly different quality. When using homemade biodiesel, it is a good idea to verify that the correct procedure was followed and that it will not crystallize at low temperatures. If any type of biodiesel is stored due to a lack of local availability or for any other reason, it should typically be used up in about six months to one year.
Biodiesel is made of triglycerides from animal fat or vegetable oil that have undergone a transesterification process. This process can result in fuel that shares many characteristics with diesel that is derived from petroleum. Unlike waste vegetable oil or other similar fuels, using biodiesel in unmodified vehicles usually causes no problems. It can still be a good idea to contact the manufacturer though, as there may be specific issues that need to be addressed.
In most cases, it is possible to simply switch over from petrodiesel to biodiesel without performing any special actions. One factor to keep in mind is that petrodiesel tends to leave behind various residues in fuel tanks and lines. Biodiesel does not contain these residues, but it can act as a solvent. This can result in many years worth of particulate matter breaking free in a short time, which may lead to plugged fuel filters. It is often a good idea to keep an eye on the fuel filter when changing over to biodiesel because it may need to be changed more frequently than normal.
Using biodiesel that was not made commercially can be a slightly more complex matter. The process of making biodiesel is fairly simple, but an inferior product may result from poor ratios or improperly treated ingredients. One tip for using biodiesel that was not professionally made is to put it in a fridge, freezer, or outside in cold weather overnight. Biodiesel tends to form crystals when exposed to extremely low temperatures, so it can be helpful to know if a batch is particularly intolerant to the cold before actually pouring it into a vehicle. Using biodiesel that is cold intolerant can cause issues, but may be perfectly safe during periods of warm weather.