.. not sure about the 4 cylinder.. but the 4.0L has molychomium (sp?) coated piston ring.. it has been our experience that anything with a smooth surface ring doesnt seat as well with synthetic oil and you run the risk of blowby in higher mileage. you can use it.. but if you find a knowledgeable nissan tech.. they will probably tell you it isnt neccesary and would be overkill.. so if that is true for the v-6 i wouldnt worry about it in the 4 cly. unless you plan on only changing every 7500 then i would use synthetic... just my $.02robher27 said:is it overkill to put this in a 2005 XE with a 4 cylinder?