A lubricating oil composition and method of operating a boosted internal combustion engine. The lubricating oil composition includes greater than 50 wt. % of a base oil, one or more overbased calcium sulfonate detergent(s) and one or more overbased calcium phenate detergent(s). The calcium, boron, nitrogen, and amount of soap are maintained within certain ratios, and the total base number contribution from all detergents to the lubricating oil composition is less than 4.2 mg KOH/g of the lubricating oil composition, as measured by the method of ASTM D-2896. The lubricating oil composition and method may be effective to reduce low-speed pre-ignition events in a boosted internal combustion engine lubricated with the lubricating oil composition relative to capable lubricating oil compositions.