In order to study the effect of low viscosity engine oil on fuel economy of turbocharged engine,five different 0W-20 full formula engine oils were prepared.Using real piston ring cylinder liner friction pair samples and selecting the key working conditions of turbocharged engine,the antifriction effect of each oil sample was tested through reciprocating friction simulation test.By controlling the WLTC fuel consumption test accuracy of the whole vehicle,the fuel economy improvement effect of each oil sample was compared.The results show that both reducing oil viscosity and adding friction improver can improve fuel economy,but the effect of the latter is more significant.The higher the dosage of MoDTC friction improver,the better the antifriction effect.Borate detergent can enhance the antifriction effect of MoDTC.By comparing the friction simulation test result with the vehicle fuel consumption test result,it is found that the friction simulation test using real ring friction pair components and setting appropriate working conditions can quickly distinguish the antifriction effect of engine oil,but it can not reflect the improvement effect of real fuel economy.