This study focused on the characterization, in term of quality, of intake valve and combustion chamber deposits collected by Toyota 1G-FE IVD test, which was developed for in-house IVD test in the Petroleum Authority of Thailand. Various analytical techniques were utilized to characterize deposits according to elemental analysis, thermal gravimetry analysis (TGA) and infrared spectroscopy in combination with solvent extraction. The results indicate that IVD contains more hydrocarbon oil and heavy fraction of gasoline than CCD, while the contents of organic oxidized products, carbonized compounds and inorganic additives in IVD are less. Resulting from hexane soluble extraction, the gasoline detergent additives in IVD are confirmed. The TGA result shows that PEA additive can be decomposed at lower temperature than PIBA additives. Comparing between piston top and cylinder head CCD, it was determined that “Oil up” phenomenon occurred at piston top more than cylinder head. The piston top CCD contains more hydrocarbon oil, while cylinder head CCD contains more oxidized and carbonized products. There was no significant difference on the characterization of deposits for the change of olefin content in gasoline and engine oil grade except for the effect on their weight. Furthermore, the analytical result of oxygen content in IVD shows that most IVD formation is resulted from oxidation reaction. Finally, concentration of metal content shows that IVD mainly comes from engine oil.