Some definitions to help visitors to TheLubepage get the full meaning of the articles, videos and radio shows available at TLP. I will add to this post over time to create a list of critical terms.

Viscosity: measure of a fluids resistance to flow.  Often referred to as weight, eg: 30 weight / 40 weight.  Using weight is actually incorrect, although there is a relationship between the weight and the viscosity it is not actually consistant or true.  This is why we see terms like light or heavy used where viscosity is being discussed.  In many cases this terminolgy communicates the desired intent of the statement about viscosity so it will continually be used even though it is technically incorrect.  I will use viscosity in all formal writing or speaking but sometimes when answering a question and the questioner has used weight I may respond using weight to avoid confusing the person asking the question.

Correct viscosity for a particular lube application is extremely critical to success.