Off topic a bit but...how long does fuel last?
Submitted: Tuesday, Jun 27, 2006 at 13:04
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Patrol22
When I'm travelling around the country I generally carry a 12ft tinny and a 9.9hp mariner outboard. The outboard is a 2 stroke job. I also carry a 12" Stihl chainsaw (usually). I generally mix up 20 ltrs of 2 stroke fuel for the outboard and a couple of ltrs separately for the chainsaw (Stihl don't recommend using oil designed for outboards in the fuel mix). Quite often I don't use all the fuel in the one trip and if the weather turns nasty can find myself bringing all the fuel
home with me. Stihl recommend that you ditch fuel more than 3 months old.....Mariner don't have any recommendation in the handbook that I can find.
Given the ever-increasing cost of fuel and 2 stroke oil I'm finding it increasing against my Scottish nature to throw "old" fuel away.....how long is too long to keep/use fuel that has been mixed. What damage will say 6 month old fuel mix likely to do etc. What do you guys do to limit waste in this regard.
mmmmmmmmmmmmm maybe i'll just have to do a bit more fishing.
Cheers
Pete
Reply By: Sand Man (SA) - Tuesday, Jun 27, 2006 at 13:29
Tuesday, Jun 27, 2006 at 13:29
Pete,
Being of Scottish
heritage myself and also owning both a Stihl Chainsaw and a Mercury Outboard (Read Mariner) I can say that I have never experienced any difficulty with fuel that is several months old.
To my way of thinking, as long a the engine starts and doesn't run rough with lots of smoke (too rich) I'll use up what I have.
For the Stihl I mix up 5 litres at a time. (Usually only use this at
home)
For the Outboard, 10 litres at a time.
As I usually have at least one 20 litre jerry of unleaded with me, I can mix up more Outboard fuel if required.
Bill.
AnswerID:
180596
Reply By: Mike Harding - Tuesday, Jun 27, 2006 at 13:37
Tuesday, Jun 27, 2006 at 13:37
From:
Site Link
8.6 What is "stale" fuel, and should I use it?
"Stale" fuel is caused by improper storage, and usually smells sour. The
gasoline has been allowed to get warm, thus catalysing olefin decomposition
reactions, and perhaps also losing volatile material in unsealed containers.
Such fuel will tend to rapidly form gums, and will usually have a significant
reduction in octane rating. The fuel can be used by blending with twice the
volume of new gasoline, but the blended fuel should be used immediately,
otherwise teh old fuel will catalyse rapid decomposition of the new,
resulting in even larger quantities of stale fuel. Some stale fuels can drop
several octane numbers, so be generous with the dilution.
--------------------
Sounds like the main issue issue is a reduced octane rating - won't bother most small engines, especially two strokes, much. I've used fuel which has sat in a plastic 25l container for over 12 months and couldn't detect any difference.
Mike Harding
AnswerID:
180598
Reply By: Member - andrew B (Kununurra) - Wednesday, Jun 28, 2006 at 21:39
Wednesday, Jun 28, 2006 at 21:39
I have similar issues myself, but the 2 stroke oil I last purchased (I think it was the yamaha or sthil brand, can't remember and the label has long gone off the bottle) was good for any 2 stroke, both air and water cooled. luckily I have an old 15hp Jono, which is very tolerant, only uses a 100:1 mix, so I don't go through much oil. I jenerally top up the mower and snipper out of the stale outboard tank, splash in a bit extra oil and don't have a problem. When we only had a Diesel cars it was a worry with fuel out of the 'big boat - only 17ft so no need for jealosy', now that we have a petrol car I put the spare boat fuel into the car and use fresh stuff in the big boat (Honda 4 stroke).
Cheers Andrew
AnswerID:
180923