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I'm going to brainstorm here so bear with me!
When the gas evaporates in the tank, it is prevented from escaping by the seal on the filler cap right?? But isn't there a line running from the tank to a charcoal filter that collects excess vapours? Or have i gone wrong somewhere? Anyway, from what i can remember, the filter then lets the collected vapours into the inlet manifold when the engine is running. But if the charcoal filter was not working correctly, would there be vapours going into the atmosphere? (Was there a discussion on charcoal filteres here before??) I'm thinking that if the gasoline level is low, there is a lot more space to hold vapours and therefore increase the possibility of more escaping. But if it was going to escape, it was going to do it anyway, regardless of fuel level. Man, this is complicated!
Thing is, by keeping the tank topped off all the time, you are then visiting the gas station more, thereby doing more unneccessary trips AND filling up more, therefore returning collected vapours more often to the underground tank in the station. Which is apparently 1%. But that's 1% of any amount, small or big. Hmmm...
I think there is a certain amount of trade offs going on here and can't help feeling like we are being had with these emails that do the rounds. I mean, we don't see such emails telling us to air up your tires to max sidewall or to slow down to 50mph do we? I think there's certain vested interests with all this. No offence to the OP mind. Discussion is always good!
ollie
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