Capacity is 296ml on my string trimmer.. Now either i mix oil with non ethanol gas but i doubt id go through a gallon within 30 days so gas will get old and sit in trimmer. I imagine that the tank will outlast one job ob my 7000 sq foot lot.. Its my first gas powered trimmer and am debating buying trufuel for 10$ for a qt. Just want trimmer to last with little maintenance and hopefully wont cause issues if i leave trufuel in it over 30 days. Not sure how much i will use it. Any advice for a first time owner? Will only be using for my own property so maybe 30 mins once a week or once every 2 weeks.