The effect of near-complete deoxygenation and polar species removal on deposition 3 propensity of a Jet A-1 fuel type, with marginal thermal oxidative stability was studied 4 in a laboratory scale approach. The fuel deoxygenation was carried out via nitrogen 5 purging and two types of bespoke zeolites were used separately in a packed bed reactor 6 for partial polar separation. The treated fuel samples were assessed individually for 7 deposition propensity, using "High Reynolds Thermal Stability(HiReTS)" test device. 8 It was found that when the concentration of hydroperoxides in fuel is relatively high, 9 polar removal is more effective way than the fuel deoxygenation in reducing carbona-10 ceous deposits.