...is the ticking in line/timing with the motor, or is it a random tick? Sounds like the valve/lifter ticking that is pretty well documented. Do a search on ticking, I'm sure you will find it. Once it does it, does it stop, or keep going? My understanding is its the hydrologic lifters. Maybe running the thicker oil is making it do it. I'd go with 10/30 and see what you get. As far as I know this doesn't seem to be a problem. Mine does it from time to time if I'm on a long trip, and the engine gets hot.