Not only for people, also healthier for the diesel : cold-pressed oil. By temperatures more than 60 degrees would reach phosphorus and wax in the oil which damage a diesel.
This oil press could also process the yield of 50 ha of sunflowers and cost 10,000 - EUR. Today are similar models already offered for about 2,500 - EUR.
When today already every better car has a Climatronic, a process control would be rather practical here. Temperature sensors to decide about war warm up or chill of the oil press and to steer the speed of the electric motor.
The engine needs about 1.5 kW, the sun delivers by a photovoltaic the power for it.