When Texaco, now represented in the marine lubricants market by FAMM (Fuel and Marine Marketing), launched Taro 40 XL 40, the lubricant was designed to address pressing field problems in medium speed engines. Three years later FAMM is in a position to evaluate the performance in a large number of engines and to compare the field results with competitive lubricants. The pressing problems arose from a series of engine design and fuel processing changes. Although aimed at improving engine efficiency and making savings, the changes resulted in a series of difficulties. The best known are engine blackening, undercrown deposits, piston head corrosion, fouling of purifier heaters, increased oil consumption, base number depletion, oil scraper ring clogging and increased piston deposits.