Metalworking fluids are used to reduce heat and friction and remove metal particles from workpieces. They are used in a wide range of applications including grinding, cutting, stamping, drawing, and milling. Metalworking fluids may also help prevent burning and smoking. The four basic classes of metalworking fluids are straight oils, soluble oils, semisynthetic fluids and synthetic fluids. Straight oils are not diluted with water and are also called cutting oils or neat oils. Soluble oils contain emulsifiers to help oil disperse in water. Semisynthetic fluids contain highly refined petroleum and a high percentage of water. Synthetic fluids do not contain petroleum and are instead made with detergent-like components.