The connecting rod (Conrod) bolts are integral components of the engine that are used to connectrnthe piston with the crankshaft through the connecting rod. If the conrod bolts pretension reliabilityrnis insufficient or excessive, deformation and fatigue failure will occur, resulting in componentrnbreakage and engine failure. At local maintenance shops, they are using different replacementrnmaterials than the initial material of the new automobile. The use of improper material is also thernproblem of engine failure. The focus of this thesis is to estimate the fatigue life of TOYOTA D4DrnDolphin connecting rod bolts at high cycle using Finite Element Modeling with the help ofrnsoftwareâ€”ANSYS 2020 Rrn2rn and MATLAB tools. The high cycle fatigue life was analyzed at differentrnpretension forces to examine the effect of bolt pretensions and determine the appropriate boltrnpretension value. The prediction of high cycle fatigue life was estimated using the Stress-Lifernapproach. Additionally, the total deformation at insufficient and excessive bolt pretension wasrnanalyzed. Then the proper bolt pretension has been selected based on the analysis. Again, thernexisting in-use material for conrod bolts was compared with those the materials used by localrnautomotive maintenance shops as a replacement. Their safety factor was identified to suggestrnwhich material is suitable for connecting rod bolts. The study results from the numericalrnsimulation show that the value of bolt pretension has a more significant effect on the fatigue lifernand total deformation of connecting rod bolts, especially at higher cycles. When bolt pretensionrnchanged from 22KN to 30KN, the number of cycles of the materials reduced. The Insufficientrnvalues (22KN) (i.e., 23KN to 50KN) of bolt pretension were applied to the model, and the totalrndeformation increased from 0.16451mm to 0.21111mm, respectively. At the value of 22KN boltrnpretension, the total deformation showed the lowest number (0.16449mm), which is thernappropriate point to apply the clamping torque. In addition, the applied 22KN to 30KN pretensionrnloads on the existing material (ARP2000), ARP625+, and ARP3.5 resulted in the fatigue life ofrn498.93*10rn6rn to 489.13*10rn6rn, 409.71*10rn6rn to 399.4*10rn6,rn and 407.59*10rn6rn to 397.29*10rn, respectively.rnFor checking the safety factor of the materials, ARP2000 has a good safety factor. The ARP2000rnhas a greater number of life cycles than the replacement materials. To avoid early failure, rntherefore, tightening of the bolt needs to be controlled, and a replacement materials selectionrnrequires scientific methods of selection.