How long does it take for gas to spoil & what is the effect on our BMW?
After searching Bimmerfest for this information and not finding it, I found indications elsewhere it takes only a month for gasoline to "spoil" by some reports (Consumer Reports, June 2005, http://xs.to/xs.php?h=xs42&d=05333&f=gasoline.gif).
I was wondering about the effect on our BMW engines (motorcycles and automobiles). Specifically, it appears that the primary component of spoiling has the effect of LOWERING the OCTANE RATING of the stored gasoline.
This I post from rec.autos.tech:
http://www.repairfaq.org/filipg/AUTO/F%5FGasoline6.html
section 6.12
"Front End Volatility
Paraffins are the major component in gasoline, and the octane number
decreases with increasing chain length or ring size, but increases with
chain branching. Overall, the effect is a significant reduction in octane if
front end volatility is lost, as can happen with improper or long term
storage. Fuel economy on short trips can be improved by using a more
volatile fuel, at the risk of carburettor icing and increased evaporative
emissions."
On rec.autos.tech, they concluded (mostly) that:
There is a "significant reduction in octane if front end volatility is lost,
as can happen with improper or long term storage".
http://groups-beta.google.com/group/...653?scoring=d&
The question for bimmerfesters is:
- How long is long term for our purposes? (Is it only one month?)
- And does spoilage matter practically for our BMW bimmers and beemers?
Note: Beemers are likely in cold-weather country to be stored for the winter which is often much longer than the one month reputed for spoiling to occur so the effect on motorcycles may be practically greater than on automobiles.
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| Reply » Gasoline spoils in the tank if unused (but what is the effect)? |
It'll be hard to start and run rough. It'll take a couple of tanks of fuel with good detergents to clean it out. Found out the hard way. Top it off with Stabil if you go away for a few months.
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| Reply » Gasoline spoils in the tank if unused (but what is the effect)? |
If you can use this as a comparison.I had a string trimmer that I didn't use for 4 years that had Stabil in the gas, put the choke on pulled the string a few times and it started.IMO Stabil is what you have to use to get these kind of results.
cheers
vern
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| Reply » Gasoline spoils in the tank if unused (but what is the effect)? |
Quote: | I had a string trimmer that I didn't use for 4 years that had Stabil in the gas, put the choke on pulled the string a few times and it started. | I still have gas in my backup generator from Y2K...  Stabil is in it and starts right up... didn't put Stabil in a mower I had and didn't use it for a year... wouldn't start until I drained the gas and refilled with new fuel.
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| Reply » Gasoline spoils in the tank if unused (but what is the effect)? |
Quote: | I still have gas in my backup generator from Y2K... Stabil is in it and starts right up... didn't put Stabil in a mower I had and didn't use it for a year... wouldn't start until I drained the gas and refilled with new fuel. | My point exactly.Stabil is the answer if you store any gas engine with gas in it!!!!!!!
cheers
vern
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| Reply » Gasoline spoils in the tank if unused (but what is the effect)? |
Funny, because the reference for octane rating is that 100 octane fuel perfomrs in the test engine the same as 100% iso-octane. And 0 octane fuel performs like 100% n-hptane, which is a SHORTER chain molecule.
For car gas, there are several compounds that evaporate or react that cause gas to go bad. Aviation gasoline does not use those compounds because of the extended storage time and really bad effects of bad gas.
I find that car gas typically develops various varnishes or thick junk that causes the problems. And I have used car gas taht is well over a year old without problems.
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Gasoline spoils in the tank if unused (but what is the effect)?