A slight leak of the crush washers.
Stop the by dealership and tell the parts guy you want two of the crush washers for it so they can be replaced.
Have your guy do next time.
174,000+ miles, 5/20/12 new ej257 short block, 8/20/11 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. Also CHECK YOUR OIL, these cars use it.