I believe this is the company that resells agromgt's oil 100%? vegetable motor oil(AMG2000):
http://www.sterlinggrade.com/
This oil, I believe, is a 20% blend of veggie oil along with special additives and other oils(whether synth/mineral unknown). I guess that the 20% blend is for "safety sake".
http://renewablelube.com/
The biggest problem with supermarket vegetable oil is that it is refined to be human consumption safe, deodorized, and to look pretty in the clear bottle. Supposedly, this is why they make weak lubricants, and why using crisco/mazola/wesson are the wrong vegetable basestocks to start with.
For example, see what these companies do to veggie oil for our FDA approved consumption:
http://www.iseo.org/dir_plant.htm
My understanding is that you need to start with the raw pressed(not chemically extracted) vegetable oil and then refine/blend it specifically for use as a lubricant. You probably won't get FDA approval "for licking dipsticks" any time soon.
If you are a rebel and want to try it, then follow the simple "safety" rules typically found on bottles of 5-10 minute distillate-type engine flushes:
Don't exceed 20% when adding your (insert whatever here) to your motor oil.
Only use your(insert whatever) flush on a cold engine. This way the cold motor oil(80%) will provide enough viscosity.
Don't drive/rev the vehicle. No real load/stress should help prevent wear.
Don't run the engine for more then 10 minutes. This way, the oil temp never rises high enough to "stress" that (insert whatever).
Also, you might want to try this test prior to turning your engine into a test subject:
Pick your vegetable oil, blend it with some old motor oil from a previous oil change, cook it in the kitchen at around 200F for 1/2 hour or so. Then, let it cool and settle for a day or two. If there is no breaking down/sludging/separation/gelling, you will probably be safe with the above mentioned 10 minute 'flush'.
