@VituVingiSana
Let me answer differently.
When you buy crude at say 40 bob a litre you need to obtain products worth more than the 40 bob to make a profit. The refinery (at least the Kenyan one) will use some of your product for own operations and then produce LPG, AGO, PMS, RMS DPK Fuel Oil and Bitumen in various ratios.
By refining crude, you have fore gone importing refined products, hence the value of the product from the refinery should more or less be in line with international prices. (i.e the profit will be Value of crude refined less the Value of the refined products obtained from the refining) With the unit value being the international price of that product plus shipping cost. (In industry parlance the imported price parity or Hydrocarbon Values)
Considering that each of the products has a different price, it is therefore desirable to obtain high value products. International prices for AGO, Jet and PMS are more or less similar hence the three will be more valuable. Fuel Oil's value is about 60% that of the other three. Hence a refinery that produces more Fuel than the AGO, DPK and PMS will lead to losses. However, a marketer will have to balance the refinery output with product demand. Hence even is say DPK has more value that AGO, there might be less demand.
To your question on Jet now
Other that impurities, statics, water content and freezing point, there is no difference between DPK and Jet A-1. Virtually all imported DPK meets the Jet A-1 specs and vice versa. KPRL produces Jet A-1 but the demand for that product (like all other products) is high (higher than PMS) as such quite a substantial percentage has to be imported)
The only difference between RMS and PMS is the octane rating which is the fuel's ability to withstand detonation on ignition. Modern engines with higher compression ratio will require high octane fuel than older engines. Additionally, new direct injection technology e.g GDI for Mitsubishi, D4 for Toyota, FSI for Audi/VW require even higher octane rating (about 95) otherwise the engine will lose efficiency in a matter of time.
Itari muting'oe ihuragwo ngi ni Ngai