Veg oil car conversion

More hassle than it is worth tbh. Veg oil is thicker and thus will not atomise and burn as well as regular diesel so it'll be a smokier fuel.

Add in the comlications with cold starting, switchable fuel supply for startup and shutdown in cold weather or preheating of fuel, and the unkowns with regard to how fuel system components, rubbers and plastics especially, will react to the new fuel will all affect the reliability of it.

Unless you are doing serious milage, then it's not worth the effort.
And as said, if it is on road use, it'll be illegal anyway.

WVO/RVO might make some kind of sense for the likes of large generators, pumps, static machinery that runs for many many hours on end day after day, week after week. For small road vehicles it is pretty much a whole load of hassle and messing and time wasting for negligible savings. It's the realm of home mechanics and experimentalists.

The biodiesel and VO market basically shut down when it was realised that instead of converting a % of the fleet into biodiesel motors, you could just blend the same target volume of biodiesel into mineral diesel and work away with normal engines. Same large scale result, less complications.

Possibly would work OK by blending. But do you really want to have the hassle of blending diesel and VO and having to deal with all the measuring, mixing and general messing and fluting around that all that will entail? By the time you've the taxes declared and paid and the time wasted on all the messing you'll have nothing saved.

Mixing and storing the fuels will also require you to have proper and safe facilities for doing so and dealing with any spills if you are doing it as part of a commercial enterprise such as a farm.

If you are buying it in bottles or drums, you are going to wind up with a lot of empties that will have to be handled, stored and disposed of somehow. At a cost.
If you are getting waste veg oil it'll be manky and you'll have to have a pretty good filtering set up to extract all the filth and water. Then too, you have to buy set up and maintain all that kit and again, handle, store, transport and dispose of all the crud and waste filters. At a cost. You'd probably also have to have a waste licence/permit.

If you are doing substantial milage, then you will generate a significant amount of waste. If you are doing small milage, then it's hardly worth the effort in equipment and time.

You see where I'm going with this?
It's an awful lot of work for little if any saving.

And for just running a farm jeep, an awful draw on your time. You'd be a busy fool.

You'd probably make better savings/gains by investing the time and effort into improving other aspects of your farming enterprise.

You could instead try to achieve the same overall emissions mitigation by trying to source a fuel supplier who can offer diesel with a higher than normal blend of biodiesel in their fuel. If you could use that across all your machinery and the jeep then you could achieve the same overall outcome with none of the work. For example, if you were running a medium sized tractor on a 10% biodiesel blend you might have a bigger emissions reduction that using VO in an old jeep.

Regular diesel, whether "road" or "green" can have up to 7% biodiesel blended into it. So depending on your current supplier, you might already be using a substantial quantity of biodiesel without even realising it.