When a crude oil is being processed, there are two types of oils that are being produced: residual and distillate. Distillate oils are purer than the residual. It is being used as high energy source as fuels. Residual oils on the other hand are the products that remain after the distillation processes. Though low-grade crude products, it has many industrial uses such as adhesives, coating/protecting compounds and in manufacturing of asphalt. Distillate oils are clearer and volatile while residual oils are darker and more viscous.
Combustion of distillate oils can be summarized as:
`C_8H_18 + 25/2O_2 -> 8CO_2 + 9H_2O`
Octane, `C_8H_18` is the major component of distillate oils. Octane number is used to measure the performance of motor fuel.
Combustion of residual oils are complicated since it is composed of longer carbon chains. There is no standard chemical equation for that. Residual oils also contain high amount of sulfur thus when converted, `SO_2` are being produced as well. Soot is also produced with the combustion of residual oils.
Residual oil + Oxygen -> Carbon dioxide + Water + Carbon Monoxide