Diesel Secret?

Yes, but their "secret" is nothing more than fuel stablilizer which you can buy at Wal-Mart, Pep Boys, etc.

You also have to add kerosene and unleaded gasoline to the vegetable oil.

Correct, and a small amount of Diesel Kleen (or similar product) to increase the cetane rating of the fuel. The kerosene and unleaded gasoline reduce the viscosity and probably help increase the cetane rating as well. Not too well versed on the actual chemistry of the end product but know this does work. I have both a 240D and 300D using a similar mixture. Just make sure your fuel lines are in good shape since veggie oil loves to have rubber for lunch. You might consider changing the overflow lines on the injectors to Viton tubing,