Engine most suitable for running on vegetable oil

[Auxiliary]

Hi everyone!

Im interested in buying an a4 or a6 from  roughly 2004-2009. I would like to know what diesel engine is most suitable for running on used cooking oil. I’ve heard that the older pump nozzle injection, pd engines are the best for this use. Because of its high injection pressure and use of several “injection pumps”. 

But I may be mistaken perhaps the common rail engines also works just fine running on used cooking oil. 

What engine is the best option for my unusual request? Also, what engine would need the least modifications to work properly? 

Pardon my English I’m Swedish. 
 

 

[RoyC]

I don't know about used cooking oil.

I used to run my Vauxhall cavalier on new sunflower oil, went ok.

Trouble was it used to leave a smell of chips every where I went Hahaha.

[Steve Q]

Definitely the 1.9tdi. the 2.5tdi fuel pump is too weak from my understanding as Ive looked into it too.  

[Auxiliary]

16 hours ago, Steve Q said:

Definitely the 1.9tdi. the 2.5tdi fuel pump is too weak from my understanding as Ive looked into it too.  

What about the 2.0 tdi it also uses the pump nozzle technology

[Steve Q]

3 hours ago, Auxiliary said:

What about the 2.0 tdi it also uses the pump nozzle technology

That I don't know. Older diesel technology like the 1.9tdi or 80s/early 90s Merc engines are best