The most important point is you need an older car with mechanical injection (before ~2005). Modern diesels with electronic injection are much more sensitive to the fuel used, as they run at much higher pressure and components have tighter tolerances.
On an older car, yes you can just dump it in after some crude filtering (e.g. with cheesecloth). I have a neighbour with an old Land Rover and he has been running it for years on cooking oil. Some people start on diesel then switch to cooking oil later. It has a higher viscousity at room temperature than diesel, so it works better once everything is warmed up.
https://youtu.be/WNJH1rikujI
The most important point is you need an older car with mechanical injection (before ~2005). Modern diesels with electronic injection are much more sensitive to the fuel used, as they run at much higher pressure and components have tighter tolerances.
On an older car, yes you can just dump it in after some crude filtering (e.g. with cheesecloth). I have a neighbour with an old Land Rover and he has been running it for years on cooking oil. Some people start on diesel then switch to cooking oil later. It has a higher viscousity at room temperature than diesel, so it works better once everything is warmed up.