Old(ish) petrol - use or not - also how does fuel ages?

[slawosz]

Hi,
I have petrol on my boat I bought before longer trip and never used - its from beginning of September. I have only outboard, so having good stable petrol is important - I don't want to clean carb in the middle of marina channel . Now I am thinking what does 'old' petrol means - I know today there are some additives in petrol nowadays and I wonder if there is some way to make petrol clean again -filtering or so- or simply donate it to someone who doesn't care about it but is using for things like garden tools etc?

 

[pvb]

I've never really believed in the theory that petrol "goes off" in storage. I used to have a petrol strimmer and a petrol hedgecutter, I just left them over winter and they started perfectly the next season. I still have a petrol chainsaw and two petrol garden tractors, again I just leave them over the winter and they're perfect the next season.

 

[VicS]

I have always stored outboard fuel from one season to the next but I always transfer it to tightly capped metal cans and only store full cans.
The idea being to prevent evaporation of lighter fractions, minimise contact with air and exposure to light ............ That is how you would store samples for lab testing

I always filter it before use ( following trouble one year early in my boat ownership years when I ended up stripping and cleaning the carb while tethered to a buoy off Cowes on a dark and windy night before I dared venture up the river) and mix it 50:50 with fresh

Engine seem to vary . Some will tolerate slightly stale fuel, some wont . My old Flymo wont run at all on last years fuel! The Seagulls will run but run much better on fresh fuel. Ive never tried my Evinrude on old fuel.
IMO its not worth the risk of using fuel that might cause trouble

 

[VicS]

Deleted

 

[TernVI]

It varies.
Sometimes old fuel smells wrong.
Sometimes 5 year old fuel is fine.
Sometimes replacing 6 month old fuel that looks and smells OK makes the difference between engine starting and not.
Some engines are fussier than others. My Chinese strimmer seems to run on most things, so I use up the outboard fuel in that.
Storing it in sealed containers helps.

If it starts on the old fuel, and then you dilute it 50:50 with fresh, my feeling is it will be OK.

I try to avoid mixing more than I need, then any aging straight petrol can go in a car and get diluted with fresh, rather than keeping a gallon or two over winter.

 

[slawosz]

Thanks. So I understand that the problem is because fractions evaporate and fuel becomes harder to ignite? So it won't clog carb, it will be rather hard to start - so when I would replace it with fresh fuel engine will be more willing to start?

Fuel I talk about was never opened after filling at petrol station and cans are full.

I try to avoid mixing more than I need, then any aging straight petrol can go in a car and get diluted with fresh, rather than keeping a gallon or two over winter.

I recently bought petrol car, as I live close to ULEZ and its easy to forgot to pay for such things (ask me how I know)... But I am a bit hesitant to put this fuel into my car...

 

[Boathook]

My Honda doesn't seem to like petrol more than a year old even when it is stored in a sealed container. I normally start the season on a fresh tank and then mix old with new at a 50 50 ratio. Last year was different and I didn't mix the fuel enough.

 

[MystyBlue2]

I have a 30L plastic tank on my boat. It only takes 2 months for the fuel to become "Less combustible" leading to hard starting and the fuel starts to turn yellow from a nice light blue as i mix my fuel with oil (2 stroke).

I've heard fuel lasts so much longer in metal tanks over plastic as there is a chemical in the plastic tanks that ruin the fuel. (Apparently)

Having said that i NEVER leave fuel over the winter or for longer than 2 months anyways as its a recipe for contamination with condensation leading to water in the fuel in the spring.

I always "Winterize" my tank, Empty, Clean out all grit and fully dry, Put it in the warm house till spring so it can be filled with fresh fuel and away she goes. I do appreciate larger boats have fixed tanks though but that is my procedure and reasons why i do what i do.

 

[earlybird]

The more volatile components of petrol might be lost over a long period of poor storage conditions. This could degrade ease of starting for some engines, but once running, things should be OK.
I recall hearing, years ago, that in winter months refineries dissolved small amounts of butane into their retail petrol to aid vehicle start-up over the cold weather period. Don't know if that's still the case, or if it's needed with modern vehicle engines.

 

[CalicoJack]

I was talking to the workshop manager at a large marina last week and he was saying that 3 months is about the limit for fuel due to the amount of ethanol in it. He added that even with a ultrasonic bath he still has had occasions when the only answer has been to supply a new carburettor, which isn’t cheap.

 

[pvb]

I was talking to the workshop manager at a large marina last week and he was saying that 3 months is about the limit for fuel due to the amount of ethanol in it. He added that even with a ultrasonic bath he still has had occasions when the only answer has been to supply a new carburettor, which isn’t cheap.

So why does my garden machinery all works fine after the winter?

 

[[3889]]

My limited experience is that I bought a boat with (at least) 18 month old petrol in plastic cans in a locker and the Yamaha 2.5 4 stroke wouldn't start with it. Without doing anything else I drained the tank and refilled with fresh petrol and it ran perfectly so I'm inclined to think that the volatiles are lost over time, perhaps preferentially partitioned into the vapour space. I suppose different engines have different sensitivities to fuel composition. Winter temperatures would minimise the effect of partitioning.

 

[dunedin]

My experience with Mariner 2 stroke is it likes fresh fuel rather than last seasons. Not a chemist so can’t give reasons, but seems to be so.

Unfortunately it is tricky to dispose of last season’s unused fuel these days. But annual maintenance of neglect plus new fuel seems pretty effective.

 

[reeac]

I always started the season with new 2T mixture for my Mariner 3.3 . I used up the old stuff in my Honda 4 stroke mower which couldn't have cared less.

 

[Topcat47]

I've yet to come across an outboard with a carburettor drain. The presence of ethanol in modern fuels does cause problems with carbs unless they are drained or the engines run until there is too little fuel left in the float chamber to allow the engine to operate. I remove and clean the crb on my Tohatsu 3.5 stroker every year I use it and drain the tank and carb anyway if it's not been used. It still likes "new" 2-stroke mix. My garden tools do not have carburettors with float chambers so are less susceptible to "old Fuel"

 

[Caraway]

The premium grades of petrol have less ethanol. At present up to 5% of petrol on forecourts is ethanol (E5).
From September 2021 E10, with up to 10% ethanol, will be available on forecourts.

There have also been reports that E10 is a less stable fuel and that this can make it more difficult to start a vehicle that has not been driven for an extended period.

So the signs are that for stuff that doesn't get used a lot, or is pre 2001 the lower value ethanol is the thing to get.
Older cars may suffer fuel line and seal problems as ethanol attacks the older kinds of rubber used. Modern fuel pipe is available which is ethanol-safe, but some older injection systems may be a problem. This only affects petrol-engines.

The DfT stated: "Having analysed the responses, we remain convinced that the preferred approach outlined in the original consultation document remains the best approach to introducing E10 in the UK. Broadly, we plan to introduce E10 as the standard 95-octane petrol grade available UK-wide.
"At the same time, E5 will remain available at all filling stations that supply at least two grades of petrol as the higher-octane ‘Super’ grade. This ensures both a wide roll-out of E10 as the standard petrol grade and UK-wide provision of lower-ethanol E5 fuel, which will still be required by some vehicles."
While the new fuel should help lower cars' CO2 emissions there are concerns about its impact on fuel economy and potential damage to older cars.

 

[Rappey]

I've found that engines will run on old fuel, say 3 years old but they cough and splutter when you try to rev the engine up.
Fuel leeches through plastic tanks. Graphics for a plastic tank like a motorbike are always perforated to allow for this.
A boat locker that's not well ventelated with an outboard tank goes black and you get jelly like substance.
Articles suggest fuel like e10 only has a 6 month shelf life.
I collected a honda 600 carb version that had been sat outside with a cover unstarted for over 3 years. Took a little cranking and lots of coughing and spluttering but it started .
It was rideable, but once brimmed with new fuel you could really tell the difference

 

[Momac]

Petrol certainly does go off and seems quicker to do so now than ever.
The petrol that was in my lawnmower over winter from last year was not so good last week. The engine was running unevenly and eventually the engine stopped and would not restart despite some fuel remaining in the tank. A top up with fresher fuel and it was relatively okay but really needs 'new' fuel .
I suspect say a 5 litre (or whatever size) can near full of petrol with an air tight lid may keep the fuel longer but the best plan is to get new petrol ad use it within say 6 months.
I try to leave my (2 stroke) outboard with little fuel in it as is possible as have experienced the same rough running on old fuel cured by adding fresh fuel.

 

[penberth3]

The premium grades of petrol have less ethanol. At present up to 5% of petrol on forecourts is ethanol (E5).
From September 2021 E10, with up to 10% ethanol, will be available on forecourts.

So the signs are that for stuff that doesn't get used a lot, or is pre 2001 the lower value ethanol is the thing to get.
Older cars may suffer fuel line and seal problems as ethanol attacks the older kinds of rubber used. Modern fuel pipe is available which is ethanol-safe, but some older injection systems may be a problem. This only affects petrol-engines.

That makes sense - i.e. the ethanol will evaporate first. More ethanol - more of the lighter end lost, and quicker.

 

[johnalison]

I have had trouble running a small outboard on year-old fuel that was cured by using new. I have also used ancient fuel in a mower with no trouble, so it seems variable. If the use is likely to be critical, and for a boat’s main engine, I would use the rest up in my car mixed with good fuel.