I have a 2001 Saab 9-5 with the 3.0t V6. It has 167k miles on it. The engine has a noticeable ticking sound from the rear bank of cylinders. It's not an exhaust leak. The ticking is there all the time regardless of temperature. It gets faster as the engine revs. I think it's a lifter or two. I have Mobil 1 full synthetic in it right now. Are there any detergents I can add to try to un-"gum" the lifters? This is just a last resort before replacing the lifters. Someone recommended CD-2 Oil Detergent but I can't find ANY literature on it. Is it safe to use with synthetic oil? Or should I stay away?