The pin and bushing interface inside each link. That internal contact is where the metal loss occurs which lengthens the chain and eventually causes it to ride up and jump the sprocket. Lubricant sitting on the outside plates and rollers does very little about it. This is why penetration is the first property to look for in an industrial chain lubricant, and why applying a heavy grease to the outside of a chain is largely ineffective.

No. The metal does not elongate under normal operating loads. What is measured as elongation is wear at the pin and bushing of every link, each contributing a small increase in pitch that accumulates across the chain's length. Because it is wear rather than deformation, it is driven directly by lubrication and contamination, and a properly lubricated chain in a clean environment can last many times longer than a neglected one.

A tackifier is an additive that makes the lubricant stringy and adhesive so it resists being flung off a moving chain by centrifugal force. Without it, much of the applied oil leaves the chain within minutes at operating speed and ends up on surrounding equipment and floors. Tackified products stay on the chain far longer, which extends the interval between applications and reduces both consumption and the mess around the drive.

In dusty, sandy or high-swarf environments. A wet oil film captures airborne dust and abrasive particles and holds them against the chain, forming a grinding paste that accelerates wear rather than preventing it. A dry film product carries the lubricant in a solvent that evaporates, leaving a non-tacky coating that does not attract contamination. It requires more frequent application but is the correct choice where the environment is the dominant wear factor.

Follow the seasonal grade the saw manufacturer specifies. Bar oil is delivered by a small pump and must flow to the bar at the ambient temperature it is used in, so a summer grade can be too thick to pump reliably in cold conditions, starving the bar and chain. Using engine oil or waste oil as a substitute is a false economy: it lacks the tackifier, throws off the bar immediately and accelerates bar and chain wear.

Bar lubrication is total-loss, so every drop applied ends up in the environment. Forestry operations, work near watercourses, on nature sites and in many public and municipal contracts require vegetable-ester based biodegradable grades for that reason, and some jurisdictions mandate them. They perform comparably in use, with shorter storage life and a tendency to gum if a saw is stored full for long periods, so drain or run the saw dry before extended storage.

Apply to the inside of the chain run, so that chain movement and centrifugal action carry lubricant outward through the joints rather than away from them, and apply to the slack side where the joints are least loaded and can accept it. Clean the chain first where old lubricant has collected dirt. Automatic lubricators give a small, continuous dose which is far more effective than occasional heavy manual application.