got some royal purple in there and its on about 3100 miles and I dont know if its the old royal purple or the new but I am having some wierd noises in the engine and fuel milage is bad so im gonna change it and have an analysis done. Ive never done it before so I need to know exactly what to do. Also any suggestions on the new oil? maybe schaffer's, but should I go fully synthetic or blend, dont care about changing intervals only drive 6-8k a year?