Kinda funny, but my break-in is over at 600 miles. I used minimal oil, 1/2 quart...probally due to a shot of ARX in there. I wanted to top-off and thicken the oil a hair without hurting CC. I had a leftover 1/2q of Syntec 5w-50 that I dumped in. (what else would I end up doing with it, seemed perfect) So, the engine was instantly smoother, revved not more freely, but smoother. 5w-50 as an additive? Anyway, this makes me lean more toward an oil thicker than 20 weight for general use.