I rebuilt my 71 Cutlass 350 after 170K. I put the last 70K on it for the past 19 years. I used nothing but dino oil, 10W-30 or 20W-50. Yes, there were lots of depoisits. Deposits were pretty much the theme of rebuilding the engine. The bearings looked healthy. Otherwise it was just change the seals, replace worn tappets and cam, and a cleanup hone.