Once the truck was cranking strong, we turned our attention to the burnt-smelling fluids. We replaced everything with Royal Purple. Again, for minimizing wear and maximizing mileage and performance, we've had good results with Royal Purple. The company is now also making oil filters, so we used that as well. All told, we replaced the engine oil, transmission fluid, transfer-case fluid, front and rear axle gear oil, and power steering fluid. Some people ask us about the seals leaking after switching to synthetic, and sure it is a possibility, but we'll take the improved wear resistance and protection against viscosity breakdown over potential seal leaks any day. Basically, we look at it as good insurance as well as possibly extending the life of our higher-mileage truck.