Hybrid Fuels ? Conversions ?

I'm looking to convvert either a Nissan four / six or a
Mazda four / six to a form of Hybrid fuel. Like taking a good running, low emissions type Sentra or 626 and adding something like a CNG Compressed Natural gas option. Anyone else out there ?

I'd like to get a diesel and run it off of vegetable oil. $10 a month for fuel sounds good.

i am actually trying an electrolysis unit in my car to run hydrogen through it, but i don't know how well it works on the mpg yet. the engine seems to run a little rougher, but besides that, nothing has blown up yet, contrary to intense criticism i've been subjected to for even asking about it.