Would someone please give me an idea of the cost to boatees of diesel
fuel in either US gallons or litres?

It would be great if someone could also give me an idea of the same in
the Caribbean - I realise that it must vary from place to place.

Also, what is the current cost of petrol for cars. When I was there
last, about 8 years ago, it seemed incredibly cheap.

When we built our sailboat we never realised just how much time we
would have to spend motoring due to lack of a decent wind - in South
East Asia and the Mediterranean in particular. In New Zealand, we get
good sailing breezes of 10 to 30 knots much of the time.

Thanks,
Peter Hendra
NZ yacht Herodotus