Two-stroke chainsaws require about 2–5% of oil in the fuel to lubricate the engine, while the motor in electrical chain-saws is normally lubricated for life. Most modern gas operated saws today require a fuel mix of 2% (1:50). Regular gas from most gas stations contain 5 to 10% ethanol which can result in problems of the equipment. Ethanol dissolves plastic, rubber and other material. This leads to problems especially on older equipment. A workaround of this problem is to run fresh fuel only and run the saw dry at the end of the work.
Separate chain oil or bar oil is used for the lubrication of the bar and chain on all types of chain-saw. The chain oil is depleted quickly because it tends to be thrown off by chain centrifugal force, and it is soaked up by sawdust. On two-stroke chainsaws the chain oil reservoir is usually filled up at the same time as refuelling. The reservoir is normally large enough to provide sufficient chain oil between refuelling. Lack of chain-oil, or using an oil of incorrect viscosity, is a common source of damage to chain-saws, and tends to lead to rapid wear of the bar, or the chain seizing or coming off the bar. In addition to being quite thick, chain oil is particularly sticky (due to "tackifier" additives) to reduce the amount thrown off the chain. Although motor oil is a common emergency substitute, it is lost even faster and so leaves the chain under-lubricated.
Chain oil is either non-biodegradeable or degradable. Professionals have to use biodegradeable oil in Germany by law.
The oil is pumped from a small pump to a hole in the bar. From here the lower ends of each chain drive link take a portion of the oil into the gauge towards the bar nose. Pump outlet and bar hole must be aligned. Since the bar is moving out and inwards depending on the chain length, the oil outlet on the saw side has a banana style long shape.
Chains must be kept sharp to perform well. They become blunt rapidly if they touch soil, metal or stones. When blunt, they tend to produce powdery sawdust, rather than the longer, clean shavings characteristic of a sharp chain; a sharp saw also needs very little force from the operator to push it into the cut. Special hardened chains (made with tungsten carbide) are used for applications where soil is likely to contaminate the cut, such as for cutting through roots.
A clear sign of a blunt chain are vibrations of the saw. A sharp chain pulls itself into the wood without pressing on the saw.
The air intake filter tends to clog up with sawdust. This must be cleaned from time to time, but is not a problem during normal operation.