© 2014, by International OCSCO World Press. All rights reserved. 2014.Purpose: The goal of this work is comparative study of lubricants with different content of nanoparticle additive to obtain material with an optimal tribological properties. Design/methodology/approach: The effects of carbon nanotube (CNT) and Si3N4nanoparticle additives on the lubricated friction and wear behaviour of AISI 4140 steel were investigated. In tribological tests, the amounts of nanoparticles added to base oil (SAE 10W40) were varied. The ball-on-disc configuration of the tribometer was used for wear testing (DIN 50324). Specific wear rate, coefficient of friction, wear scar depth were measured. The wear surfaces were analysed using scanning electron microscopy and surface profilometer. Findings: Results showed that with the addition of nanoparticles, wear rates of AISI 4140 steel were decreased. The best additive content of synthetic oil was 0.05% CNT + 0.05% Si3N4(mass fraction), and in this case, the friction coefficient and the wear rate were decreased 15.2% and 76.4%, respectively. Research limitations/implications: Obtained lubricants are characterized by tribological and frictional properties but homogeneity of lubricants should be improved because of agglomeration. Farther works will be continued also for different contents of lubricant. Practical implications: Tested lubricants can be applied among in industry where wear and friction properties are important. Originality/value: Nanoparticle additive oils which have excellent tribological properties can be very attractive for automobile industry. New type of lubricant mixture (CNT and Si3N4) is used in the paper.