Propane dissolves in the other higher-molecular-weight hydrocarbons.
Not that it won't come out of solution, but it's not _that_ fast.
(Think of hydrochloric acid, which is hydrogen chloride (a gas)
dissolved in water; or ammonia (another gas) dissolved in water. Some
of it is always evaporating, as long as the concentration above the
liquid is lower than equilibrium.) Lots of hydrocarbons (mostly the
lighter ones) evaporate all the time, which is why we have the carbon
canisters in the first place. And the venting to atmosphere (as far
as what remains in the fuel tank) is equivalent to venting through the
canister; as far as the atmosphere is concerned, it is a whole 'nother
story.
But after all that, it is true that older fuel will have different
characteristics than a fresher fuel; it's just more than evaporating
propane causing the difference.
Donald.
> From: rtriplett@bjservices.com
> Date: Tue, 5 Oct 1999 15:19:00 -0500
>
> > > You can eliminate the carbon canister, but you will have to run the
> > > vent line to somewhere that it won't vent fumes inside the car. And by
> > > all means do not plug it up. The car will soon stall when a vacuum
> > > develops inside the fuel tank.
>
> Somebody correct me if I'm wrong, but don't refineries nowadays add propane to
> gasoline in order to raise or lower the octane rating of fuel (its cheaper
>that
> way)? Since propane is normally found as a gas, I just wonder what affect
> venting a gas tank to atmosphere might have on its octane rating over time.
> Since I normally drive my TR only occasionally, I always get fuel at the time
>I
> drive it, just enough to cruise around some. This way I keep fresh fuel when
> I'm driving. I wouldn't recommend keeping a low tank for everyone, but I
>live
> in the desert, so humidity is no problem.
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