Experimental and simulated quantitative thermal stratification evaluations of a small un-insulated oil storage tank subjected to heat losses during charging are presented. A model for simulating the thermal profile in the storage is developed. Simulated results using the model are found to be in reasonably good agreement with experimental results. The thermal gradients along the height of the storage are evaluated as function of the charging time. The thermal gradients are also evaluated as a function of the difference between the average temperature of the storage tank and the ambient surrounding temperature which signifies heat losses. The thermal gradient is seen to rise to a maximum value at some instance of time and then start to drop as thermal de-stratification in the storage tank starts. Parametric results using the model are also presented. The effect of the ambient temperature and the heat loss factor on the thermal gradient of the storage tank is investigated. Lower ambient temperatures and lower heat loss factors are found to increase the thermal gradient of the storage tank during the period when thermal stratification is increasing. (c) 2013 Elsevier Ltd. All rights reserved.