Butane and other low vapor pressure hydrocarbons are added in the winter to
increase the vaporization of gasoline at low temperatures. The mixture goes
to longer carbon chains in the summer to do just the opposite. More
important job for you is to stabalize the mixture and stop secondary
reactions that leave icky stuff in the fuel system. Open your gas tank and
smell. If it's sour and bad smelling you probably need to add stabilizer.
As a side note I told this to a friend for years. He had no problems for
ten years on a car that was driven less than 1000 miles per year. This
spring required a complete carb clean. Mixing new gas with old is a great
idea to raise the octane back up to usable levels. I've also found that
lower octane fuels seem to have a longer shelf life. The additive package in
high octane seems to really do some damage to the fuel over time.
> 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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