This study presents the numerical investigation of the fluid flow and heat transfer characteristics for three different high viscous fluids (Engine oil, Oil (SN-500) and Ethylene glycol) flowing inside horizontal rotating tubes. A computational fluid dynamics (CFD) methodology using ANSYS FLUENT 14.0 is used to perform the numerical analysis by solving the Navier-Stokes and energy equations through the viscous model at all cases of rotation Reynolds numbers and Reynolds numbers. The investigation is conducted at rotation speed of 25, 50, 100, 500, 1000 and 2000 rpm and Reynolds number ranged between 5 and 10 for Engine oil, 54 and 109 for Oil (SN-500) and 425 and 849 for Ethylene glycol. The results revealed that, enhancement of heat transfer in the tubes with Ethylene glycol (lower viscous fluid) increases slightly with the further increase in rotation speed. This is because of the viscous effects which are observed significantly larger in the tubes with Ethylene glycol than those in the tubes with Engine oil and Oil (SN-500). These effects weakened growing of the tangential velocity component in the flow. In the tubes with Engine oil and Oil (SN-500), the maximum values of thermal performance factor are found at rotation speed of 1000 rpm, whereas, in the tubes with Ethylene glycol are occurred at rotation speed of 100 rpm. The value of the maximum thermal performance is about 2.1 for tube with Engine oil at a Reynolds number of 10, 1.6 for tube with Oil (SN-500) at a Reynolds number of 109 and 1.44 for tube with Ethylene glycol at a Reynolds number of 849.