Stale fuel? Explain

[Metal Doctor]

So whats the deal with stale fuel???

heard this so much "could be stale fuel mate"

At what point does fuel become "stale". i know if you leave it in your carbs for too long without running the bike it turns to goo, but how old does it have to be before it affects the performance of the engine??

[bogan]

Depends on the volume, if you have a full tank, it'll last for months with no change (I do this with pre-mix for my dirtbike and 3 months is good). Only a few liters in the tank and a month or two could see it turn to shit. The carb fuel goes off quicker, but you get fresh stuff through quickly so no bother, and it'll take ages to turn to varnish.

I'm sure there is some chemical explanation, but the practical one is enough for me.

I've never had stale fuel in a 4T, but my 4Ts are generally used weekly, had it on my 2T dirtbike, felt like it was 'hunting' for the powerband but couldn't quite find it.

[Akzle]

the evaporative stuff evaporates, leaving the less-volatile shit. (goo, or, after a few years, hard resin)

[FROSTY:Me]

Our petrol in unzud is such rubbish it needs octane boosters to get it to work. over time the boosters "flash off" leaving very low octane fuel that bikes don't seem to like much

[Metal Doctor]

thanks for the explanations!

a couple of people told me that NZ fuel was a bit shitty, never had any problems my self, but my dad could smell that it wasnt great fuel!

[schrodingers cat]

Get a glass jug and put a litre in. Sit and watch it for a bit.
Look at all the wafty goodies wafting away.
Bye Bye exciting wafty bits. Hello stale remaining bits, I guess its just you and me now the excitment has left

[Ocean1]

thanks for the explanations!

a couple of people told me that NZ fuel was a bit shitty, never had any problems my self, but my dad could smell that it wasnt great fuel!

There's three types of fuel in NZ. Stuff out of Marsden point, made to recognised international standards, Imported stuff, made to recognised international standards, and blends of the above two.

By far the most likely to be causing any trouble is the imported stuff. For a while we got quite a bit of Russian stuff, it definitely smelled different, and usually arrived with an unusually high water content.

And the difference between brands in NZ? It all arrives down the same pipeline. Any difference can only be in the additives, usually well less than 0.01%, and usually arriving in the same container, from the same supplier. You work it out.

And yes, the evaporatig thing is correct, petrol isn't a single chemical, it's a range of chemicals split from an even wider range: crude oil. The more volitile elements evaporate more quickly, leaving a range of chemicals some motors might struggle with. How long tha takes depeds on temperature and how much air circulation there is within the tank. That's why modern cars have sealed tank caps with small pressure/vacuum break valves built in.

[caspernz]

There's three types of fuel in NZ. Stuff out of Marsden point, made to recognised international standards, Imported stuff, made to recognised international standards, and blends of the above two.

By far the most likely to be causing any trouble is the imported stuff. For a while we got quite a bit of Russian stuff, it definitely smelled different, and usually arrived with an unusually high water content.

And the difference between brands in NZ? It all arrives down the same pipeline. Any difference can only be in the additives, usually well less than 0.01%, and usually arriving in the same container, from the same supplier. You work it out.

And yes, the evaporatig thing is correct, petrol isn't a single chemical, it's a range of chemicals split from an even wider range: crude oil. The more volitile elements evaporate more quickly, leaving a range of chemicals some motors might struggle with. How long tha takes depeds on temperature and how much air circulation there is within the tank. That's why modern cars have sealed tank caps with small pressure/vacuum break valves built in.

C'mon now, don't be giving away too much of the insider info...

How long before someone asks how to check the opening pressure on the PVV, that's if they can locate it...

[Metal Doctor]

Ok heres a one for all you knowledgeable folk!

is high octaine racing fuel normal fuel with shit loads of booster in it, or, is it a more refined cleaner fuel?

Thinking of getting some.

[Brett]

Definitely goes stale....my lawn mower proved this. I was mowing are rather large lawns and ran out of fuel. We live a little bit away from the nearest fuel station and I had some old (like 2 year old) fuel sitting in the back of the garage which I thought I would give a go. Well, it ran for about 5 or 10 minutes and then suddenly died. When I pulled the starter, the blade spun freely - ie no motor compression. Pulled the head off and sure enough, one of the valves was stuck open! (rather tightly too!). Got piston free, oiled it up a bit, chucked in fresh fuel and away she went.

[Ruahine]

Ok heres a one for all you knowledgeable folk!

is high octaine racing fuel normal fuel with shit loads of booster in it, or, is it a more refined cleaner fuel?

Thinking of getting some.

Do you mean trying 98/95 over 91? I wouldn't bother unless your bike is designed for 95. Octane rating relates to the fuel's ability to self-ingnite under compression. Higher octane being more resistant. I don't think the higher octane is any "cleaner" or "refined".

[Ocean1]

Ok heres a one for all you knowledgeable folk!

is high octaine racing fuel normal fuel with shit loads of booster in it, or, is it a more refined cleaner fuel?

Thinking of getting some.

Octane booster? It's simply one of the chemicals that usually make up petrol anyway, they just add more of it. Octane ratings are largely bullshit anyway, a calculated performance value, rather than any level of "goodness". Even ACTUAL Octane rates are simply indicitive of another more accurate performance value, knock rate, which is the actual range of conditions that the fuel will detonate at.

Racing fuel has a slightly higher knock rate, and because of the additive used to make it that way it's not strictly speeking "lead free".

And unless your engine is specifically designed to run racing fuel the most likely performance change will be that you'll fuck it.

[caspernz]

Ok heres a one for all you knowledgeable folk!

is high octaine racing fuel normal fuel with shit loads of booster in it, or, is it a more refined cleaner fuel?

Thinking of getting some.

Sssshhh, but last time I delivered a tanker load of AvGas to a facility that decants from 35,000 litres into more consumer friendly sized containers that read "Racing Fuel" it was just that...AvGas.

For any roadgoing vehicle, if you want the highest performance fuel, just use 98 to save yourself the hassle of engine dramas...like Ocean1 already mentioned

[baffa]

Do you mean trying 98/95 over 91? I wouldn't bother unless your bike is designed for 95. Octane rating relates to the fuel's ability to self-ingnite under compression. Higher octane being more resistant. I don't think the higher octane is any "cleaner" or "refined".

I hope you arent running your CBR on 91.

Any vehicle with high compression or a turb should be running 95+.
Even slightly nanaspec cars made in Japan are designed to run on higher octane.

There was a great article by the self appointed Gods of motoring, the AA recently basically saying anything greater than 91 is a waste of time. If you beleive that, you are as stupid as they are.

[Metal Doctor]

i always run all my bikes on the best i can get at the pump, i never use 91.

i was thinking about using racing fuel in the KTM on the dirt, i've heard about some guys using it, and i can smell it when i go riding. A fella told me you can buy it from ardmore air field or a service station in pukekohe sells it. apparently some guys mix it 50/50 with 98ron, and someone told me you need a racing licence to buy it! i have no idea if any of this is true!

so is high octain racing fuel and Avgas the same thing then?