Lubricant films under extreme confinement at nanometer scales play a crucial role in lubrication engineering. Improved understanding of squeezing and friction behaviors of such ultrathin films can lead to strategies for preventing surface failure and efficient national energy usage. Through computer simulations we show that lubricant films under compression can solidify below some critical monolayers distance. Under sliding friction these solidified films exhibit stick–slip friction in which the slip occurs at solid–lubricant interfaces. However, dilation of the lubricant during slips (a signature of shear melting) is never observed, which is consistent with other experimental findings. These insights, with strong support from surface force balance experiments, may open the way to improved lubricant design.