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Originally Posted by willd
Stale fuel.......how long does petrol (gas, sorry guys  ) take to go stale?
And if it did, i'm presuming it would just be absorbing moisture from the air in the tank.....what would the symptoms be?
I'm just wondering about my own, it's been laid up in the cold months and I haven't re-fuelled, and it's idling badly.... |
Euro gas (petrol in Brit speak) is more highly refined than US gas. Unfortunately that also means it goes off sooner - 30-35 days vs 35-60. This can be extended by using a fuel stabilizer to 3-4 months.
Moisture absoption is an issue, but the real problem is that gasoline is a very chemically unstable compound. It changes over time. Gums and varnishes (parafins) come out of solution plus the octane rating drops. When this happens, the fuel is less able to withstand compression and combusts too soon causing knock, ping and general poor starting/running.
Fortunately, is doesn't take more than a couple gallons of fresh fuel to somewhat 'revive' the old fuel making it at least capable of running the car and being burned.
Whether you use stabilizer or not, it's a good idea to keep diluting older gas by short-filling it 3 or 4 times before emptying the tank.
Cheers!