Another thought is would it be cost effective at today's prices.
1 Gal. of Walmart Great Value $6.74
1 Gal. of Diesel Fuel average $4.00
Didn't used to be that way but with the inflation of shipped goods, the cost of vegetable oil is higher than diesel fuel even without taxing it.
So can the everyday diesel engines of today run on vegetable oil.... The answer is yes! So why don't we? The first deterrent is that the US government has a strict law against it. Why? Well in the US the government taxes the fuel used in cars and does not tax food, so it would be bad for business. There is a big and healthy fine if you are caught trying to do so. This is why all the myth busters and testers out there perform there tests with used vegetable oil or fryer grease they obtain legally from a restaurant.