I thought about fitting a a pug HDI engine and then converting it to run on vegetable oil and fitting it in a Murena before I went and bought my car...
That would really have given me the best of everything.
Cheap fuel, good looking car, great reliance to rust, and good mileage, and decent performance.
But in the end.. you can buy A LOT of petrol for the cost of such a project.
And you need lots of time and mechanical know how,to attempt such a project

Maybe a project for some crazy Dutch??
