Abstract: A method for extending the interval between lubricant changes in an internal combustion engine. A small volume of lubricant is removed from the engine at periodic intervals and combusted within the engine. Clean replacement lubricant is provided to replace the portion of the lubricant removed from the engine. A connection is provided between the lubricating circuit and the fuel supply system. The flow of lubricant through the connection may be controlled in response to the measurement of a quality perimeter of the lubricant. Replacement lubricant may be provided to the engine from an onboard storage tank.