Hi,
Yes you can mix small quantities of veg oil in with you diesel, just put in the tank, although I would not recommend high leval's without conversion, Especially with the Lucas Cav Pumps. Doing so will stress your injection pump considerably due to the high viscosity of veg oil when not heated. This could result in failier or a reduced life of your pump (and they are not cheap). You should look at doing a dual tank conversion or at least fitting a heat exchanger (not electric glow plug type) We manufacture Veg Oil Heat Exchangers our web site is
Sunshine Fuel - Diesel to Vegetable oil conversions Sorry to plug our site, but if I can be of any assistance with your conversions then please let me know.
Regards
Mike Gaylor