stale fuel

[Guest]

Just had the embarrassment of taking the outboard (Yamaha 8hp 2str) out of the boat, down to agent as it just would not start, only to be told it was 'stale fuel'. Sure enough, new fuel, perfect performance. Only filled the tank 6wks ago. I thought this only happened if you left it over the winter! What goes wrong? Is it condensation or what? How can I avoid it? Also seem to be stuck with the fuel as the car has cat. converter.

 

[Chris_Stannard]

You may have filled the tank but where did you get the fuel from. Two stroke mix, when left in your can goes stale after a while. It seems I think that the oil in the mix tends to go into globules which gum the works up. The answer is not to take too much mix a time, or to mix some unleaded, with two stroke oil in a jug just before you fill the outboard.

Chris Stannard

 

[VicS]

I accept that fuel goes stale but not that quickly.

I always keep fuel from one year to the next but I transfer it from my plastic tank to steel cans and only store full cans. I filter the stored fuel through a fine filter and mix 50:50 with fresh before use. The only time I had trouble was when I didn't bother to do this.

I have also had the last bit of 2 stoke oil in the bottle go off when kept for several years.

I have 2 possible theories:-

1. That some of the more highly volatile components can be lost through the walls of a plastic (polyethene) container.

2. That air can diffuse in and result in oxidation of some components.

Any oil industry Chemists out there with any knowledge of what the causes fuel to deteriorate?

 

[Freebee]

Frost auto restoration sell fuel preservative claimed to prevent oxidisation in petrol for 2 years. anybody tried it?

 

[webcraft]

I've flown microlights with fuel that's been standing for over a year and lived to tell the tale. (Did give it a bit of a shake first though).

The mix was 50-1 with fully synthetic oil though, which probably makes a difference.

- Nick


BlueMoment.Com
http://www.bluemoment.com

 

[oldharry]

I'm not a fuel chemist as such, but my understanding is that petrol stored for more than two months or so starts to undergo a chemical change as the more volatile fractions dissipate, after about six months in store it can (but not always) have 'decomposed' sufficiently to prevent starting.

The effect varies depending on the engine - particularly the compression ratio, and the level of tuning. A 'soft' engine - low compression ( say, 7:1 compression ratio), and low level of tuning may be unaffected, while a higher compression engine ( 9 or 10.1) with more sophisticated carburation may not run at all. This applies to both 2 and 4 stroke engines.

Mixing old fuel with fresh in modest amounts will avoid wastage, and is unlikely to damage anything but the most highly tuned units. I usually dump any left over outboard fuel in the car tank just before filling up so that it is well diluted - and never more than a gallon to a tankfull (but not just before MOT testing as the emissions will go up with the 2T oil!).

 

[VMALLOWS]

But preferably not in your diesel car................ (won't do much harm though at less than 1:10 ) Best answer is to keep sailing all year!

 

[Guest]

2T fuel in any amount into a car engine especially that of todays cars is not something I would advocate !! It must do wonders for the Cat Conv. and other bits and bobs !!

I run Petochem labs and to be honest most of what I read is b----s ...... fuel stored properly in tight closed and in dark / cool place will last for years .... the biggest problem is loss of aromatics and degradation due to light.

When we sample gasoline and similar fractions - we have to use coloured bottles and with double closure to prevent light degardation and also gassing off of the light ends.

Most petrol containers used in UK etc. are very poor storage containers for gasoline and actually for gasoil / diesel as well !

When we get to fuel tanks on engines etc. they have to have vents to function, even with the air-screw type filler caps these leak sufficiently ....

QED me ol' fruit !

 

[Guest]

Tight closed / drak storage ...

Oxidation Stability is a factor of degardation due to oxygen and also light.

Dark room and a tight closed container will be cheaper and just as effective.

 

[Guest]

Getting it right !!!

Gasoline and Diesel have changed significantly over the last few years, particularly due to reduction of Lead and Suphur levels allowed. This has had an immediate effect on Octane and Cetane Ratings along with lubrication.
The producers and middle-men have come up with wonderful concoctions to remedy the drop in 'burn capability' by adding various fractions / components to boost the fuel. Most of these are highly vaprous and free venting fuel will lose them quite rapidly .....

Question to all out there ..... Has anyone noticed a change in petrol smell when filling the car ?? It's stronger and far more difficult tio remove from clothes and hands after splashing etc. This is due to all sorts of additives like : MTBE, ETBE, Pyrogasolines, Pyrocondensates etc. etc.

Now anyone wishing to store gasoline should remember - cool, dark place and keep the lid tightly on !

I have fuel in my outboard from months ago and it still works OK ... I have containers of spare fuel over a year old - still works ...... my boat and acr stand for long periods during my travels / work etc. - they still start first kick etc.

What you do not need is more additives and crap in the fuel !!!!

 

[Guest]

Light - Oxygen - Heat nm

**

 

[DavidTocher]

I use two stroke mixes for my Vire 6HP (20:1) and my Seagull (10:1) with straight SAE30 oil and never have any problems. The Seagul will start 3rd or 4th pull with petroil left in the tank up to 3 years. The Vire always starts at the beginning of the season with the old fuel left in the tank from the previous year.

I do however always run the engine dry of fuel by shutting off the fuel. This avoids oily residues in the carb.

My guess is that the oil or air cooled two strokes is different to that used in watercooled engines. Straight oil doesn't have anything fancy added.

 

[Joe_Cole]

I don't think you should put old 2 stroke fuel into a car which has a catalytic converter....I think it ruins it.

If I'm wrong then please let me know.

Joe

 

[VMALLOWS]

Re: Getting it right !!!

I have to admit I have not experienced any problems with either 2-stroke mixture or straight unleaded stored for at least a year in either the outboard, strimmer, or (4-stroke) lawn mower. All stored cool/dark/metal.

As for smell, don't buy enough petrol to be able to comment.............but the smell of (particularly) marine diesel varies from 'hardly at all' to 'stinking of shellfish'! All seems to work fine though.

 

[Guest]

Thanks to all for interest. The comments have made me realise I've had this happen since changing to cheap plastic tank which sits in the open. I'll invest in smaller metal one (no light, ?no leaks) and will regularly top up with fresh. Fingers crossed!)

 

[Guest]

Sae 30 ??

Standard Lub oil is unstable in a petroil mix and not advised ... but then you are using older engines that tolerance is wide ... the Seagull and Vire's ... they run on vodka and cooking oil if necessary !!!!

For more modern styles I would not recc'd it !

 

[Guest]

Re: Getting it right !!!

You have shwon that it works and I can only agree ... being in the business so to speak, I know that I can buy and use gasoline many moons after. Diesel is a different matter as it is not so vaporous and volatile as gasoline. It does not have such aromatics and generally can be stored more casually.

The only real worry with diesel is making sure that any water is reduced to absolute minimum in storage to reduce risk of bugs developing. Note that any diesel stored for long period should be decanted slowly and without stirring up bottoms .... the bugs die after quite a short life and collect in the bottomm as black sludge. This sludge is insoluble in any medium that I am aware of. Various additives claim they dissolve it, but generally they only break it up into minute particles suitable to go through the combustion cycle without clogging filters / injectors.

 

[Guest]

Be careful with your Cat

Cats are very expensive to replace ..... and I would never put any fuel in that would compromise it ..... 2T and other oils are definitely NOT what the Doctor ordered for a Cat !!

I used to pour the odd ends into my old Landrover 2.25 petrol job ..... but that was a 1953 vintage job and it loved it !! I even used the old egine oil from my 'family car' to top up the sump when necessary between oil changes !!!! The Service guy used to give me stick about it .... but knowing that oil is normally still good Visc. etc. when changed, and also if it comes out of a good engine it will not do much harm to an old long-stroke thumper like the LR engine !!

 

[DavidTocher]

Re: Sae 30 ??

What do you mean by 'unstable'? As far as I can tell the mixture hasn't changed from its original state when mixed.

The tanks I use are metal and light proof whic may be significant. the Seagull tank is sealed when idle but the Vire's tank is vented.

 

[chriscallender]

Re: Getting it right !!!

One thing I have been wondering about diesel and bugs - is there any benefit to leaving the tank full or nealy empty over the winter. Any ideas on whether I should fill right up with fuel just before the boat comes out the water???