Unleaded petrol - how long does it last?

[danthecapriman]

Just wondering what the general opinion is about unleaded petrol, how long can I expect it to last and still be usable?

 

The reason I ask is, my Mercury is refusing to start, having tried everything I can think of to get it running the only thing I can come up with is the petrol has gone off. I bought the current petrol when I picked the car up in September last year. It has run perfectly on it since then but the last few times I've fired it up (started a couple of times over the last few months) it has gotten progressively worse and worse running. But now it's extremely difficult/impossible to start.

 

So am I expecting too much for the petrol to last some 7 months?

[saucedoctor]

Funny, I was thinking about this today as I was trying to get my strimmer started. ISTR it mentioned on RR that petrol starts to go off after 3 weeks.

 

Regardless, 5 litres of fresh pez saw my strimmer belching smoke and annoying the neighbours dog.

 

Also, all modern fuels iz shit.

[willswitchengage]

ISTR it mentioned on RR that it starts to go off after 3 weeks.

 

It's probably worth noting that seeking information from RR has similar factual credibility to listening to drunk people singing outside a nightclub.

 

Incidentally our electric lawnmower started perfectly this afternoon after being laid up for six months.

[M'coli]

Autumn petrol will contain fewer volatile distillates than winter/spring petrol too, so that won't help.

[DS20]

My petrol lawnmower started as normal after five months of being unused.  Car engines might be more susceptible to stale gas than lawnmower ones, perhaps?  

[xtriple]

I 'believe' that it does go off remarkably quickly nowadays. Bikers and boat owners are having real problems wakening their prized possessions from the winter slumber!

 

It's supposed to be that the higher aromatics boil off really quickly and leave you with a tank full of useless crap. Worse if the tank is vented or the cap is a poor fit as on old cars.

[spike60]

I always thought most of the start problems were because the galleries etc inside the carb or fuel pump etc were dry after standing. I recently started a Husqvarna chainsaw after 5 years and it ran fine on the fuel in the tank but was a pig to start at first.

[Squire_Dawson]

Around six months seems about right. I'd say it would last for longer but obviously it's better to fill up with fresh juice. Yank engines would surely be more tolerant of stale petrol within reason?

[dave21478]

Modern petrol is properly pish.

 

I have a lot of 2-stroke garden tools that I use a lot for my job..... various chainsaws, strimmers, hedge cutters, leaf blower etc etc as well as a few 4-stroke mowers, rotavators, generator etc. They range from brand-spanking new to older than I am, from cheap Chinese pish to big brand names.

Within the last few years I have found its pointless to keep any petrol over winter when most equipment isnt being used - come spring time they are impossible to start and run poorly when going. Put some fresh stuff in and off they go with no hassle.

It affects cars too. I had about 15 litres in a drum that I wasnt going to be using. It had sat for 4 months or so - I chucked it into the C2 and it ran like a bag of shite, cutting out at idle until I filled it up with fresh stuff.

[danthecapriman]

Thanks for the replies.

 

The more I think about it, having read this is that it must be the cause of my problem. Strange though that I've not experienced it before in any of my other cars.

 

I'm going to try to get some fresh petrol next week and drain the old stuff out. Anyone want about 20+ litre of old petrol!?

[tooSavvy]

Incidentally our *electric lawnmower started perfectly this afternoon after being laid up for six months.

 

Do you get your erictrikkerry from Wales.... could have been sitting about, in an old slate mine for bloody weeks!!

 

You wuzz lukkie M8

 

 

TS

[dave21478]

Garden tool places round here sell octane stabiliser additives which are supposed to keep fuel good for long periods over winter etc. I have never bought it so  dont know how well it works or if it would be economical for use in a car thats to be laid up for a while.

[Bren]

Bikes are more averse to stale fuel - some simply refuse to start.

[Fat_Pirate]

I left a tank of super unleaded in my MX5 for nearly 18 months, without issue.

[Taff]

Thanks for the replies.

 

The more I think about it, having read this is that it must be the cause of my problem. Strange though that I've not experienced it before in any of my other cars.

 

I'm going to try to get some fresh petrol next week and drain the old stuff out. Anyone want about 20+ litre of old petrol!?

I kep a 5 litre can in the F and I use/refill it monthly-ish.

 

On the other hand, May Galaxie has been parked up for months with the same half tank of gas, making my a pointless hypocrite

 

Hope this helps?

 

 

tapped on the radiator using morse code

[danthecapriman]

Trouble with mine is it's got just under a quarter of a tank in it. Maybe this lack of volume hasn't helped with it going off - condensation inside steel tank etc? Apparently a fuller tank will last a lot better.

 

Way I'm feeling about it at moment I'd like to pour petrol on the car and burn it to the ground!!

[RayMK]

The majority of people who use cars infrequently seem to blame the fuel for starting problems after several months of layup.  My own experience with my 1961 Reliant is that it has no noticeable effect on starting until the fuel is at least a year old.  At that age, the stuff looks horrible, like brown soup, and tends to block the carb jets.  Unleaded will readily absorb moisture from the air, aided and abetted by day/night temperature cycling and vented tanks. This encourages corrosion inside typical mild steel car tanks (hence the brown soup), as well as evaporation of the volatiles.  It stays clear and works well for much longer when stored in sealed jerrycans.

[steve_earwig]

Ah crap, is this why I've had no luck with any of my 2-steokes this week? They're all antiques so I expect one or two of them to give me trouble but this is ridiculous, the petrol's from about November I think (the 4-stoke tiller works fine on it).

 

That's a plan for tomorrow then, buy 10 litres of finest INA unleaded crap, mix 2x5 liter cans, one at 50 one at 25, tip old fuel in Toyota (it deserves it).

[alf892]

Spent 3 hours trying to star my lawnmower yesterday. In that time I took the carb off 3 times gradually taking more apart to cleaning it. It was running poorly at the end of last year.

 

After the third carb strip and removing and cleaning the air tube the reason suddenly occurred to me. Just fore I had trouble with it last year it ate it's (rotten) foam air filter so I replace it with a bit of foam I had lying around.

 

On inspection this foam was closed cell. Cheapskate repair failed........much time wasted. Bit ashamed to confess this tbh.......I am a time served mechanic (not a fitter or tech!) so it shouldn't have taken that long.

 

Oh.....the fuel from last year was fine.

 

The only time I have had problems with fuel has been petrol boats......dad Alf buys up disused ones and flogs them on.....for some reason once they sit for 5 years or so they won't fire up on stored fuel although they will run on it once started.

 

Given your fuel is only six months old I'd be surprised if that was your full problem

[Timewaster]

Ah see Alf, I did a proper bodge and simply threw the filter back in the shed and left the mower to free breath.

 

My idea worked sort of.

[Taff]

Dan, bung 10 litres of fresh in there, see if that helps

 

 

tapped on the radiator using morse code

[strangeangel]

Bikes are more averse to stale fuel - some simply refuse to start.

 

My experience has been that it's pot luck, my cousin's YBR125 had to have the tank and carb drained before it would go after being sat for just a few months, yet last week I went to a bike I SORNed 12 months ago and it fired straight up on the stuff in the tank.

[danthecapriman]

I'll take the Gerry can to work with me tomorrow and get some while I'm out and about. 20 odd litres of new unleaded fed directly into the carb should prove this one way or the other!

[Uncle Jimmy]

The garden strimmer type problems aren't necessarily due to the fuel loosing it's combustible properties; more due to the ethanol content, at least that's what the garden machinery guru told me- a varnish builds up around carburettor jets causing the starting issues.

I've had no problems using six month old petrol in the Ovlov; maybe because it's older and lower compression?

[fred]

8 months in a rangey - fired up but was so shite back firing,cutting out etc..  chucked another 2 gallons of fresh in mixed up with the pallooky old stuff kicked up fine

[forddeliveryboy]

I'm told that unleaded is techincally good for 3 to 6 months, which in reality seems to mean that after 18 months you may well be stuffed. 4* used to be fine after 3 and more years, apparently. The ethanol bollox means more probs for some, depending on how old/fuel line materials.

[Station]

I emptied the petrol out of the tank in my Starion which was 11 years old and put it in my Micra and it ran fine.

I think it's good on carb cars, but never tried it on FI cars.

I did put petrol diesel mixed in my Nippa and it didn't complain.

[Coprolalia]

Word I've heard is it's something to do with the increasing ethanol content. The ethanol evaporates off/ reacts and leaves nasty deposits. Doesn't seem to be as much of an issue for injection cars with low compression, but carbs get full of the deposits and gunk up. Scirocco runs like a pig after being left for a while, but a top up with Super and she runs fine.

There's an episode of Roadkill where they pull an engine apart that's been sat for a year or so and won't run, and it's gunked with dried ethanol stuff. California has about 10% ethanol, 90% alkane/alkenes. We have on average 5%/95% for the last ?10? years. Since March 2013 there's been 10%/90% about as well, but they have to advertise.

I think basically if your petrol is 5+ years old it's probably more stable due to a lower ethanol content, whereas if it's a year or so old it's junk. Depends on ratios and your injection/carb/fuel pump of choice as well.

 

Full really in depth info: - http://www.groups.tr-register.co.uk/wessex/ethanol-update.html

[cros]

I use Briggs and Stratton Fuel stabiliser on small engines with only a bit in the tank. But how do I know if it works? I've had engines start after a year without use, so I'm probably wasting my money. With bigger petrol cars I syphon the juice out of the tank if its left for more than a few months- a complete pain but most people with old tat seem to do it because of fuel going off. Then your tank rusts. Maybe Quentin can end this misery.

 

"If your fuel is going stale you’ve really got to try adding my piss. I know these magic cure-alls have been around for ages, but this one really does work. A mate’s Bentley S2 wouldn't start, but rather than swallow the two grand hit for an overhaul, he dumped into the sump. My waste products are not cheap, but it’s a very sound investment."

 

 

[plasticvandan]

3 months is what ive always believed for modern ethnic peace unleaded. not like the 4 star that was in an MZ i bought that hadnt run for 10 years (10 years ago) it fired and ran on that!