RE: Why castor oil?
The VW rabbit diesel was deplorable for lack of performance. The last time I rode in one about 1985 and wanted to kick with my feet to get it going. It was a poor excuse for a car.
About the same time I rode in a Chevette diesel that had an Isuzu engine. I must say that it was very nice compared with a gasoline Chevette. I really liked it.
A guy at work had a Chevy S10 diesel that was an Isuzu and it seemed pretty nice too. He used it until the body wore out.