A well-lubricated chainsaw is crucial. If it isn’t oiled, heat will build up from friction, the saw will need more gas, and the chain won’t turn as fast.
Most saws are self-lubricating. There is an oil reservoir in the housing from which oil is pumped out using the same crankshaft assembly that turns the chain. Oil is pumped into the groove in the bar. As the chain runs, it lubricates itself and the bar.
Check the oil level when you refuel the saw. Use chainsaw oil. It is cheaper than regular oil, stays on the chain better, and has better sling characteristics. Using old motor oil is not a good idea since it has metal particles in it and may dull the chain.
Each chainsaw manufacturer has specific requirements for the fuel and oil mixture. On professional saws, the fuel oil mixtures are as high as 50:1. On less expensive saws they can be as low as 25:1. All fuel/oil mixtures must meet the manufacturers' specifications.