I do it. Here is what I do. I collect used Veggie oil. I make sure they arent using hydrogenated, It has a tendency to gell.
I blend cleaned veggie oil with diesel 50/50 and as high as 65/35.
I collect the oil in 30 gal. drums, they are easier to handle by yourself than 55gal.
I transfer it into a heater tank, heat it to 140 deg. Let it set for 24 - 48 hrs.
Drain it into a filter tank. I have 2 drains in the heater tank, one 6" off the bottom fot the oil and one on the bottom for the sludge.
After it goes to the filter tank, I push it thru a 2 -5 micron filter with an electric pump in to clean 15 gal jugs.
At this time I add 6 oz of Cetane booster. This brings the cetane up to prevent excess smoke. 6 oz of cetane will treat a whole tank. I also add 4 oz of staybil to help drop out any excess water in the oil. Let this all sit another 24 + hr.
When Im down to 1/8 tank I add 15 gal of oil and top off with diesel.
This is a whole lot easier than making Bio or the Diesel Secrets formula. And this works good, same power and performance and same fuel mileage. Just smells good. I started this back in oct of 05 so it has been almost 1 year and about 25k miles. The only drayback is it tends to clog fuel filters quickly. The high acid in the oil cleans the varnish or parafin out of the fuel system. I by filters off of ebay at 11.00 ea vs 28.00 from autoparts store.
Last thanksgiving We went to Cloudcroft NM and I took 45 gal of oil with me and blended it at each fillup. I averaged 18mpg going and got 21mpg coming back. I got down to 8 deg and I was a little worried but it ran okay.
FYI , Diesel Secrets used a blend of 80% oil, 15% diesel, 5% RUG( reg unleaded gas) . I elimenated the gas from my mix because gas in a diesel engine causes coking, which isnt good for diesel engines. If you want to read about it further do a google search.
I run a 2000 F250 4X4 CC 7.3L Powerstroke. Air Raid Cold air intake, 4" turbo back exhaust, no cat, Micro Chip Programmer, Pilar gauges( pyro, boost, tranny temp).
Just for grins I went to the Drag races one night this summer and my best time was a 16.7. Not too bad for a 7400# sled. It was fun but smoked my tires too much and got yelled at for tearing up the track, switched to 4X4 so it wouldnt spin so much. And I was running veggie oil blend.