My Cruze is ticking its way toward 85,000 miles and running like a sewing machine. Valvoline Synpower every 5K and Seafoam in the tank every 10K is all the engine related fluid maintenance I've done, but I wouldn't mind doing a light crankcase cleaning since it's getting close to 100K. BIL did Seafoam in his TDI Beetle's oil a few weeks ago (Schaeffer's 9000 5w40) and it smoothed out a lot. However, I'm hesitant to do so with my little 1.4T that doesn't have the most resilient turbo and is a hard-working, hot running gas turbo rather than the (at least in my mind) lower performance, more tractor-like turbo diesel. Is there any danger in running the recommended amount of Seafoam in the crankcase for 500-1,000 miles before an OC? May not make any difference in performance, but idle hasn't been as smooth lately as it once was and if the process won't endanger the lubrication of the turbo then it won't hurt anything.