<human>:  When should I use a lubricant?
<bot>: Lubricants are used when there is friction between two surfaces. This can be caused by a variety of factors, such as when you are using a tool or machine, or when you are engaging in sexual activity. Lubricants are used to reduce friction and prevent damage to the surfaces. Lubricants are also used to reduce the risk of infection and to make sex more pleasurable.