Hi grant, welcome, you will see many posts from me over the past month, I am a noobie and had the same questions but with new veg oil.
Mine is running currently on 40l of ktc veg oil (new at 79p a litre)
And 3.8 litres of petrol (to thin the mix)
In a post i made last night i posted up interesting mixing facts and gelling points of different fluids. Veg oil goes into a gel at 0 degrees so a spirit or petrol must be added to make the gelling point way below freezing and to thin the mixture.
I also shake my truck every morning before I get in :lol
She smells wicked and I have no performance difference what so ever.
Nor have I had to change the fuel filter (i believe you do on used veg oil though)
Chuck some in and give it a go, you wont go back :thumb2
Also as you will find here fixing your terrano is practically free when you join up on the forum, the guys here and the knowledge available is better an the dealerships (not to mention the care too) oh god I'm getting all emotional again