How good or bad for your engine is that?

Not that I use anywhere near enough cooking oil for it to be a benefit.

Really depends on the engine. If you have common rail injection, then it's a big nono. The viscosity of the oil is much, much greater than diesel and will quickly ruin things.

My truck has an engine that's largely unchanged from the 1960s design and it really doesn't care what you put in it (within reason). Cold weather can be an issue as the viscosity increases with temperature, but I've heard of people near Aberdeen running 50/50 mixes all year round without issue. Others go for a two tank setup, running on our diesel until engine up to temp then switching to pure veg.

Mot testers like you to have pure diesel in for the Mot, as otherwise the test station ends up smelling like chips for weeks.

 :-D

You lot have that advantage over there as we have fewer diesels than we should. I especially like the Rover TDis and we are (the NAS market) finally getting one next year!!

Do folks add kerosene to the vegetable oil to thin it? I think that's what I'd do, add a couple of gallons of kero to cut the viscosity down.

Nope. When your engine is hot it's fine (viscosity is a function of temperature) and a two tank system uses pure diesel to get up to temperature. Otherwise mix it in the tank with diesel and it's thin enough.

Of course I'd never do that in practice, as that would be tax evasion. Even if veg oil is half the price of diesel, I'd never consider it, Officer.

I have seen set-ups with a heater element in the cooking oil tank to warm it up before use

"seen"?

well, seen discussed online, but I think there were photos etc

(nod)

Your secret's safe.

Not from the feds.

<Feds> Don't bust his door down yet. We need better evidence. Follow him and check the exhaust for an odour of chips. </Feds>