How long does fuel keep its octane rating?

[Evoluzione]

And what is a good octane booster to use?

I brimmed the tank on my snotter for a mapping session which was unexpectedly (there is always something though isn't there?!) cut short due to the 750 injectors maxing out.
It may end up being 3 - 4 weeks till It goes back with bigger ones fitted and I am worried about falling short of the mark due to stale fuel.
Any ideas folks?

[anonymous-user]

Octane actually increases over time

[andyiley]

I don't know about octane, as that is a specific measurement, but I DO know from experience that as the "light ends" (most volatile & therefore easiest ignited) of the fuel slowly evaporate over a period of time the fuel does become less easy to ignite.

Having said that I am talking months rater than a few weeks.

I think you will probably be ok.

[stevieturbo]

Given fuel would sit in a stations tanks for 4 weeks or more...especially SUL etc, I hardly imagine it would be any concern after such a short time.

I know my own car has sat for months with the same fuel in it and never caused me any issues

[BliarOut]

Just got my bike back on the road after six years. Fired up straight away on the button and done fifty miles on six year old fuel with no problems

[shoehorn]

My bike can sit for months on old fuel and never miss a beat.
My Mondeo 2.5(5 cyl) had been unused for a couple of months last year and had a low rpm hiccup/hesitation/misfire which cured its self after fresh fuel was added/mixed in.
This year the same thing,while remaining unused the half tank of fuel left once again seemed to be producing a low rpm hiccup,this time I let the fuel light come on first and after re-fuelling the hiccup once again vanished.

The same again with my lawn mower/tractor,a real bd to start on old fuel and then takes a good ten minutes of running by holding the governor and revving the nuts off it before it will idle.
A drop of fresh petrol and its transformed(it`s had no blades since 2004 but its still good fun for whizzing round our field on and will still remove long grass to some degree

[kimducati]

Different operating environment I know, but when we used to run 100cc 2 stroke karts, the super unleaded would 'go off' noticeably after a couple of weeks. I have also had a 'fresh' can of fuel from a garage give problems - obviously an old batch. The motors would have a very noticeable hesitation out of corners and would also lack top end power. They were obviously much more extreme than a normal road engine, running up to 22,000 rpm!
Kim

[randomwalk]

I left my car for 2 years and it started up as usual, did not notice any change. I had read lots of info about fuel going off however in my case it was all good.

[84Dave]

Over her in the U.S.of A., I've used a product for years known as 'STA-BIL'. A fuel stabilizer & performance improver. An 8-ounce plastic bottle 'treats' 20 gallons of fuel. If the fuel in my jug/cell/race car is planned to sit for over 30 days,I use it. www.sta-bil.com. Works for me! -Dave-