What the mix of oil 4 5 liters of petrol gas gas 125?

It seems there might be a misunderstanding in your question. If you're asking about mixing oil with petrol for a two-stroke engine, the typical ratio is commonly 50:1, meaning 50 parts petrol to 1 part oil. For 5 liters of petrol, you would need about 100 ml of oil. However, please verify the specific requirements for your engine, as different engines may have different oil-to-petrol ratiOS.