Grease is a semisolid lubricant composed of a base oil, thickener and an additive. It has a high initial viscosity that keeps it from dripping or running and makes application easier than oil. It can also be formulated for many different environments including extreme temperatures and pressures, and various loads and speeds. Grease is ideal for lubricating parts and machinery that cannot be lubricated frequently and where oil would not stay in place. It also offers protection against corrosion and moisture. The base oil of grease is generally petroleum or synthetic. Grease thickener is often soap, and it imparts either a solid or semisolid consistency onto the grease. Additives can improve lubricity or resistance to pressure or high and low temperatures. Grease is available in high and low viscosities commonly expressed in an NLGI (National Lubricating Grease Institute) grade. Lower NLGI grade numbers indicate higher viscosities and better flow. Grease may also be graded as safe for use in food production environments.