[michaelovitch]

Yes, mixing with diesel.
Petrol is not appropriate for a diesel engine in my opinion.
The quality of the combustion will drop.
it's the exact same thing that if you mix petrol in diesel fuel in stock conditions
To have max benefits of the VO (its a nonsense to dilute petrol that you bought, to run on "free" fuel while you are obliged yet to buy some diesel fuel for start the car ) i suggest you to heat it up till you have the same viscosity as diesel fuel.
In winter you will can start on diesel and once hot enough switch on VO.(VO that you must heat up in any case)
The straight starts on VO are possible but really risky if you use an electric heater in the very proximity of the pump and in fuel filter.
otherwise you will break the pump.