Old Petrol ( how old is too old)

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mikehibb

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Until last year, I was a raggy and as long as my diesel tanks were kept full, we never had a problem over winter.
Last year however we changed to a 21ft buddy with new 115hp Evinrude Etec outboard ( 2 stroke with remote oil tank).

Due to a change in weather at the end of last season we were not able to burn off all the fuel that we had hoped for, despite a magnificent blat around for an hour just before lift out.

We have a 100 ltr tank, but still have about 30l left in from last year.
New tank etc, clean fuel, boat has been lifted and stored indoors so no condensation problems ( also in a considerably warmer country than UK)

So as the as this is just over 6 months old, would we be able to just fill the tanks and dilute the old with new, or should I just get the tank drained by the yard and fill up with new.

Thanks in advance

Mike
 
We have an old Peugeot 206 which must often sit around with the same fuel in the tank for 6 months and it never misses a beat. Also I've never yet bothered to burn off the fuel in any of the lawnmowers before storing them at the end of the season and I've never had a problem. Could be your Evinrude is more delicate, of course...
 
I think you should get away with your plan if you are adding 70pct of new fuel, but it can be a serious problem.. It is always better to use fresh fuel, and from a reliable supplier that has a good turnover.

Most people don't realise that gasoline is a mix of lots of different hydrocarbons (unlike diesel which is fairly homogeneous) so it is always inherently unstable.......LPG is added to the mix to aid cold starting, which will always be the first part of the mixture to evaporate. This is the main reason you may have starting problems using 'old' fuel.
With current EU Fuel regulations, the mix must also contain at least a 5pct 'bio' element.
In gasoline this is usually ethanol.....which unfortunately is very hydroscopic and absorbs water very easily.
It will absorb water from the free air in your fuel tank, also from the free air ( or residual water) in the fuel supplier's land tank from which you have just filled!
The longer you leave it, the more water it will absorb. At higher the ambient air temperature (med climate?) there is more water in the air ready to be absorbed.
I'm not an engineer, but water and fuel systems don't tend to mix......if left it can cause a lot of corrosion in the fuel system.......... and it certainly doesn't burn!
 
sarabande said:
there are a number of additives which claim to help petrol survive being stored.

http://www.ebay.co.uk/sch/i.html?_f...ol.TRS0&_nkw=petrol+additive+ethanol&_sacat=0


Lots of the local foresters and gardeners use Briggs and Stratton Fuel Fit. Seems to work well on my hand held machinery using ethanol rich fuels.

http://www.briggsandstratton.com/eu/en/support/videos/other-engines/briggs-and-stratton-fuel-fit

For £3 or so a 250ml bottle treats 100 litres.
Click to expand...

I've heard many stories about old petrol. Never had a problem myself ( I recently put 40 litres of 4 year old petrol out of 2 X 20 litre jerry cans into my car, it runs fine).

2 stroke petrol seems equally stable. The only issue I have had was with a Ryobi motor; the fuel lines in the fuel tank basically broke up into many pieces; very brittle, like chalk. I can only assume it was due to ethanol. The replacement tank has different hoses, TPU I suspect.
 
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My outboard, small 6 hp 4 stroke does not like old petrol that has been heated in the summer, and the "lights" have evaporated off. My old lawn mower will tolerate the lower calorific petrol. My feeling is that yours will be fine, if left over the winter, as it should not have been hot enough to evaporate much off. Stick a bit of fresh fuel in and off you go.
 
Bought a new petrol strimmer 8 years ago and at the time mixed 5 litres of petrol with 2stroke @ 40 to 1 and still using that same can of fuel now, its almost gone but never been a problem. Have left outboards, jet skis etc in garage with fuel in for many months and never had a problem.
 
I leave my fuel tank with a lot more fuel than that and have never had a problem, even when not topping up with new fuel.
 
aquapower said:
Bought a new petrol strimmer 8 years ago and at the time mixed 5 litres of petrol with 2stroke @ 40 to 1 and still using that same can of fuel now, its almost gone but never been a problem. Have left outboards, jet skis etc in garage with fuel in for many months and never had a problem.
Click to expand...

Your garden must be in a terrible state !

Get out there & sort it out :)

You will be fine. If possible fill the rest of the tank up with fresh.

Henry :)
 
henryf said:
Your garden must be in a terrible state !

Get out there & sort it out :)

You will be fine. If possible fill the rest of the tank up with fresh.

Henry :)
Click to expand...

:) it only gets run for a couple of mins while I trim where the mower won't reach, could really do it with shears but having something with an engine is much more appealing.
 
Not sure about 2 stroke and fuel may have changed in the past 10 years but when we bought our old boat with twin AQ431b's it had not been started for three years.

Fired up as soon as the fuel got to the plugs and as there were almost full tanks I ran about for a few weeks on it. Never an issue and when filled with fresh after there was no difference in performance.

We had that boat for 7 years so it does mean we are talking about petrol from 10 years ago.
 
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