How long does fuel maintain its octane rating b4 it starts dropping??

octane rating does not decrease as fuel gets older. Octane rating is fuels resistance to ignition which actually increases with age to the point that it doesn't burn and cuases a lean condition.

Hillbilly,my understanding has always been the key ingrediant to higher octane numbers is tolulene and as gas sits it loses octane as the tolulene and other addittives evaporate,everything i have ever read cautions you to keep gas no longer than 2 weeks if you expect it to be 100% of what it originally was. I think thats a stretch but I am cautious about gas that is a few months old or older.. I always add some race gas in the spring if i had gas all winter in my boat as it will melt down if it doesn't have 92 octane in my blower motor. I have seen teauge and crockett say this also the supposed 2 stroke snowmobile experts also caution against using gas that has been sitting too long,especially if in a gas tank such as a boat or race car where it is vented to the atmosphere,Smitty

I would also like to know about this. I have alway heard as Artic said. The octane goes down with time and will cause detonation if you don't allow for this change.

Octane does drop over time - after 60 days of summer heat - it is much lower than manufactured. Octane rating is a way of comparing the fuel to the burning of an octane (8 carbon branched chain hydrocarbon) - The octane rating is made of two numbers - a research number and a motor number - Thats why it says (R+M)/2 - it's the average of the two numbers - a fuel with an octane rating of 100 will be just like octane - for reference - diesel fuel is in the 40-60 range and racing fuel is up around 112. If you run a motor with fuel outside the octane range deisnged for, it will detonate - as the octane number drops - the more likely a fuel is to detonate - combust just because of compression. I always add stabilizer to the tank if it is going to sit for more than a couple of weeks.

. I always add stabilizer to the tank if it is going to sit for more than a couple of weeks.[/QUOTE]


This will maintain the octane rating?

so if you had a 55 gal. barrel of 110 sitting around for a year, how much would the octane decrease? if i mix 55 gallons of 87, could i use it in my car?

Not if the racing fuel is leaded and you car has a catalytic converter.

I put everything in my truck that I won't run in any of the toys. Two stroke mix, 116, gasoline I drained from a diesel pickup truck that was about 30% diesel.

Fuel Stabilizer Helps To Maintain Octain Rating?