how long can i leave petrol in the tank before it causes problems

bill, June 2010

Incidentally the shelf life of current unleaded fuel is approx 3 weeks. After this time it will deteriorate very quickly and can/will impede starting of small engines.

Also remember any left over fuel in a fuel can also need using up or disposing of. Don't make the mistake of going to the effort of running an engine dry if you're not going to be using it for periods of 3 weeks or more and then filling it with old fuel in your petrol can when you come to use it.

Incidentally- earlier cocktails of fuel was of much greater quality and therefore the shelf life was a lot more that present day brews. If Maurice has been with machinery for as long as he states then it stands to reason he will have been using better quality fuel in the past and would go some way to explaining why he hasn't had many starting problems. Todays unleaded fuel is of such poor quality it doesn't stay stable for very long at all.

pleasant, July 2010

As I said
Ideally during the winter you should drain off/ use up the fuel before cleaning the machine and putting it away for the winter months.This is best practice.
Yes I guess I have been lucky having owned 4 machines of my own over 34 years plus looked after my Dad's mowers for another 13 years.
Only problem I ever had was when there use to be cork seals on the fuel taps lack of petrol over winter use to dry out the cork seals over winter and the fuel tap use to leak a bit on first filling in the spring!

Maurice, July 2010

Maurice talks like an idiot whos been lucky. Run every engine completely dry- it's not the left over fuel in the tank that will cause problems in the spring- it's the fuel left in the fuel lines and carb that will cause you problems.

pleasant, July 2010

Ideally during the winter you should drain off/ use up the fuel before cleaning the machine and putting it away for the winter months.
That said I have never followed this advice and have never had a problem. I normally find that following the last cut of the season there is only a small amount of fuel left in the tank and it has evaporated by the spring time.
Come spring use fresh petrol.

Maurice, June 2010