I have 1 - 2 liters of unleaded petrol that I use for my lawnmower. Last time I had it serviced, the guy said not to use petrol that had been left to stand all winter due to something to do with crystallisation in the fuel and problems it can cause in the engine of the mower. I have checked with the local waste disposal and they mention that they offer a collection service for this, but it is £40! I'm not paying that for a couple of liters of fuel. What are my other options?