I omit water requirement as not important.
Should you crack oil?
You can transform 2 heavy, 2 petroleum or 1 light to 1 solid fuel.
You can crack oil products: 4 heavy → 3 light → 2 petroleum.
Heavy oil gives you 0.5 solid fuel per heavy unit. Heavy cracked to light gives you 0.75×1 = 0.75 solid fuel per heavy unit.
Light oil gives you 1 solid fuel per light unit.
light cracked to petroleum gives you 0.66×0.5 = 0.33 solid fuel per light unit.
Result: You should crack heavy into light, but avoid cracking light into petroleum.
Basic or advanced oil processing?
Best values you can get per oil product unit: heavy → 0.75 solid fuel, light → 1 solid fuel, petroleum → 0.5 solid fuel
Basic oil processing gives 3 heavy, 3 light and 4 petroleum per 10 crude.
Advanced oil processing gives 1 heavy, 4.5 light and 5.5 petroleum per 10 crude.
Total solid fuel per 10 crude:
- Basic oil Processing: 3×0.75 + 3×1 + 4×0.5 = 7.25 solid fuel
- Advanced oil Processing: 1×0.75 + 4.5×1 + 5.5×0.5 = 8 solid fuel
Result: It is better to use Advanced Oil Processing to maximize solid fuel yields.