How long does it take for petrol to go "off"?

[Casper]

Just curious, has anyone got any information on how long it takes for premium fuel to go "off" and lose its kick?

Reason I ask is I hardly ever drive my XR these days (I'm either interstate or working from home so no need to) and its not uncommon for it to sit for weeks on end without being driven.
At the moment its got a little over 1/4 of a tank in it which was put in back in mid December (yup, Ive used less then 3/4 of a tank in over a month) and I'm curious to know how long before it goes off and at what rate it degrades.

[Grechie]

im also interested in knowing this, i was told shell optimax was the worst to go off real quick

[rodderz]

Not sure how long it takes to go off but I remember back when go kart racing a lot of the guys were adamant about only opening there fuel containers for a short a time as possible, storing it out of sun and heat and using it as quick as possible to keep the octane rating up as close to what it was new.

Probably wouldnt make a great deal of difference in a car if it wasnt for months on end but i spose in a racing situation people are chasing 10th's of seconds

[MO]

About six months but as soon as you put in a fresh batch..your back in business.

[AlbertM]

I worked with small industrial engines if they sat for more than 3 months they were very hard to start. Replacing the fuel picked them right up.

[Bill_R]

I'd think sediment settling might be an issue if it is left for an extended time.

[Casper]

so based on the above... it starts to degrade immediately (as expected), loses a noticeable edge in about 3 months and goes to crap after 6 months?

[plext]

I had always used a rule of thumb of six months, but have heard people claiming that as short as a month may have an effect.

Interestingly, it seems that oil giant Chevron agrees with none of this:

Storage, including storage involving gum formation, does not change the bulk properties and most of the performance characteristics of gasoline (excluding the characteristics affected by the gum itself). For example, storage does not change a gasoline's anti-knock index (octane) or energy content. However, these properties will change if the storage is accompanied by evaporative loss. The evaporation of light ends decreases a gasoline's antiknock index and increases its energy content.

Full page here

[Green X]

Most Oil Company’s guarantee their Fuel for 1 year if stored correctly

You can buy a product that you add to the fuel to make it last for quite some time.

The best bet is to just keep the tank near full or full to keep condensation from forming in the Tank.

[fmc351]

Link 1

Link 2

Some people have too much time on their hands

[Ruger]

It all has to do with how its stored. if its stored in a tin on the shelf itll keep for a long long time but in a tank it would de generate pretty quickly i try not to leave mine in their for more than a few weeks

[Casper]

Well, for the good of the car, I'm going to take it out tomorrow and burn up that old fuel as fast as possible. :evil3:
Time for a fresh batch.

[ebxr8240]

haha like you are looking for an excuse ??? Lol...

[uranium_death]

Just read the use-by-date.

[thefargo]

great thread, and it has reminded me that I have 20 ltrs in my backup generator that hasn't been started for over 2 years. I guess that will get a run tomorrow!

[OLDFORDNUT]

with generators you should run them every 3 months even if just to be assured they will work when needed,all two stroke motors inc outboards should have petrol shut off and carbs ran dry before being put away as the two stroke oil breaks away from fuel quite quickly leaving sludge in bowls and jets stuffing them up,after about 3 months ,

[brenx]

The higher octane fuels go off faster. I noted differences in easy of starting within 2 weeks with Mobil synergy and BP ultimate.

[MITCHAY]

Originally Posted by ebxr8240

haha like you are looking for an excuse ??? Lol...

Who needs an excuse to drive their pride and joy? :

[normxb]

Hey Casper

Somewhere here I have a "write-up" on a Back-up disk about Fuels from a guy who works for BP technical dept. , and brentx is pretty right . Deteriation starts from 2 weeks . (been looking for the disk & can't find it ATM.) as soon as I can find it , I'll post it up .

Originally Posted by brenx

The higher octane fuels go off faster. I noted differences in easy of starting within 2 weeks with Mobil synergy and BP ultimate.

Also never fill your car when a tanker has "just dropped off a shipment" , it has been found some companies deliver "warm fuel" . When the fuel cools off there can be a difference of 2,500L (less) per tanker . I know this would have a very small effect in a car fuel tank but a $ is a $ .

( If anyone has other 1st hand knowledge , please correct me if I'm wrong )

Norm

[peterban]

Originally Posted by Casper

Well, for the good of the car, I'm going to take it out tomorrow and burn up that old fuel as fast as possible.

I must remember that if I ever get pulled up for speeding!!!! :

[MITCHAY]

Originally Posted by normxb

Also never fill your car when a tanker has "just dropped off a shipment" , it has been found some companies deliver "warm fuel" . When the fuel cools off there can be a difference of 2,500L (less) per tanker . I know this would have a very small effect in a car fuel tank but a $ is a $ .Norm

I tend not to fill up after a tanker because it stirs up all the crap, so I've been told.

[ronwest]

A couple of years ago my daughter was overseas for 6 months. Her car sat outside for that time. Gave the battery a charge the day before she arrived home and it started and ran no probs.

You want stale fuel?

I used to import motorcycles form the US (usually old Triumphs, Nortons etc) The fuel was supposed to be dumped prior to shipping but quite often a bike would arrive with a couple of litres in the tank.

Never tried to start any with stale fuel but I can tell you that after 30 years there's not much colour or odour left...

[normxb]

Wow , Ron

THAT is OLD fuel

I've got an old racecar & have to give it "a kick in the guts" every now & then , if it's been sitting 3 mths or so all it will do is belch flames out the exhausts but will not start till I've put a few litres of fresh stuff in .

MITCHAY

Yep , that could be a problem too ,

Norm

[Steffo]

The oldest fuel story I know of is my dad's old Econovan. A year and a half it was parked in the same place with the same full tank of 91 RON, and then it was started, driven, etc, with no real difference to any other 91 RON filled up afterwards.

[MITCHAY]

Originally Posted by normxb

Wow , Ron
MITCHAY

Yep , that could be a problem too ,

Norm

Particularly in Boxer engines ing_sm

Only fill up at one petrol station here.

[normxb]

Steffo

Could depend on the "Specs" of the motor too , years ago I had a BMW (Blue Mazda Wagon) 1981 , 1400 Mazda Van , & it would run on nearly anything . Once I ran out of fuel on my cousins farm & filled it from an "old" can from their "bush-basher" , it got me to town .

[[Tonko]]

Originally Posted by ronwest

A couple of years ago my daughter was overseas for 6 months. Her car sat outside for that time. Gave the battery a charge the day before she arrived home and it started and ran no probs.

we had a mitsu wagon, left here when a distant relative went over seas, so it sat under a tree for 3 1/2 years, with a flat tyre and cobwebs everywhere, same 1/4 tank of fuel, (i siphoned most of it!) chucked what we thought was petrol down the carb, it was diesel, then some metho, she smelled a bit but after that there was plenty left to drive it to the wreckers... :eclipsee_

[woodsy109]

Originally Posted by normxb

Hey Casper
Also never fill your car when a tanker has "just dropped off a shipment" , it has been found some companies deliver "warm fuel" . When the fuel cools off there can be a difference of 2,500L (less) per tanker . I know this would have a very small effect in a car fuel tank but a $ is a $ .

( If anyone has other 1st hand knowledge , please correct me if I'm wrong )

Norm

My brother worked as dispatch manager at BP and I can guarantee that they don't deliver "warm fuel". There may be a slight difference in temperature as in most cases the fuel is stored above ground at the depot and then underground at servo. This would be 1 or 2 degrees at most not enough to make a noticable difference. About a year and a half ago BP started taking into account temperature when selling fuel to servos so that the final litre amount charged is adjusted by a temperature correction. This means it makes no difference if they deliver "warm fuel", they still won't be making any more money from it.

And MICHAY is very correct about not filling up after a tanker has been. Not only is there sediment in tanks, but there can also be quite a lot of water.

[MITCHAY]

Well after learning how much a new engine of my type costs, I'm definately not going to skimp on petrol quality! Even second hand would well and trully sink me .

[Joes_meat]

I started our old 84 Honda Civic after four years of sitting in one spot. Started first go. Did blow a lot of smoke for the first few minutes though. Ran the same as always.