Engine oil plays a critical role in lubricating moving parts within an engine and protecting against harmful deposits forming in the exhaust system. In 2-stroke engines, oil is mixed directly with fuel to ensure correct lubrication during operation.
For Stihl 2-stroke engines, a common mix ratio is 1 part oil to 50 parts fuel. To calculate the correct amount of oil, divide 1000 by the mix ratio to get the millilitres of oil per litre of fuel, then multiply this figure by the number of litres of petrol being used.