Thanks for the writing assignment... i'll type up something...
WMO For 6.9/7.3 IDI's for Dummies:
Waste motor oil, properly processed, is an excellent fuel source. It has more chemical potential energy than diesel, and no modifications are required on a Ford IDI engine.
Cut the oil:
Two natural properties of pure oil are counterproductive in diesel engines... the high viscosity and high flash point. By adding in about 15% gasoline (RUG, regular unleaded gas), you can counteract both of these undesirable qualities. I do my mixing in 5 gallon buckets with a paint mixer paddle on a drill.
Settle the oil:
Gasoline, time, and gravity will help the oil "settle." Water, which is heavier, will sink to the bottom. Gasoline helps to knock some contaminants out of suspension, and they'll sink to the bottom. Cutting with RUG before settling decreases the time needed for impurities and water to settle out.
Filtering the oil:
Filtration is the key. Most people starting out with WMO won't be jumping straight to a centrifuge, so I'll focus on conventional filters. Three common types of filters are sock, spin-on, and household water.
Sock filters can be used by simply hanging it inside of a bucket, and pouring oil through. Housings for use with sock filters are fairly expensive, and they are best used for a rough pre-filter (~100 microns) when pouring oil between buckets or very small batch processing with a 1 micron filter.
Spin-on filters use traditional automotive style filters, but finding ones with a low enough micron rating (1, ideally) can be difficult and expensive. Water-separating spin-on filters are fairly easy to obtain, and make for a simple addition to help separate any residual water.
Household water filters and housings are very economical to use for filtration. Ideally, you want to filter down to 1 micron, so your last filter should be a 1 micron absolute filter. Since household water filter housings can be found in pairs or triplets, I'd recommend multiple filters before the 1 micron element. This keeps the more expensive 1 micron filter from getting clogged by much larger particles.
Currently I run a 20, 10, 5, and 1 micron filter, then a spin-on water separator.
Gravity vs Pump:
Gravity works, albeit very slowly, to push WMO through your filter assembly and is perfectly acceptable when starting out with WMO. Pump driven assemblies can use an electric all in one pump, such as the Harbor Freight clear water pump. These operate best when gravity fed, to avoid priming issues. PVC pipe or clear vinyl tubing available at any home improvement store works perfectly fine with oil.
Storage:
HDPE containers work just fine for storing oil. These can range from simple 5 gallon buckets to several hundred gallon tanks. When pulling from a large tank, it's recommended to draw from a couple inches off the bottom to avoid the dirtiest, settled part of the oil. Never use the very bottom layer of gunk/sludge if you're using small buckets.
Use in a vehicle:
During the summer I was able to run W85 (WMO cut with 15% RUG) exclusively. Startups weren't an issue on oil alone. For winter use, I start/shutdown on diesel in the rear tank, and switch to my W85 in the front tank immediately after starting.
Tolerance to oil will vary, cautiously experiment with your vehicle to find what it likes.
Transmission or hydraulic fluid will burn good as well. Avoid heavier gear oil, and any diesel/water emulsion.
