fuel octane question for someone that knows

[the gman]

OK I understand my 89 110 Rude only requires 89 octane but I can get NON ethenal 89 or 91 octane. My question is where I don't get to run my boat as often as I would like, does fuel lose octane as it sits so buying the 91 be safer as to knocking.. And does the 91 burn slower so the 89 would get better throttle responce????? Don't mind spending the extra for the 91 but just want to know if I am hurting performance...THANK YOU

 

[adam98]

Re: fuel octane question for someone that knows

87 is not hurting performance. if anything gaining some...but you "shouldnt" be able to tell. low octane burns an a lower flash point so it fires faster and unless your compression requires 91 there is no need for it. I doubt these motors ever have a JUST knocking problem due to old gas, it will not run well if the gas is that old .they only turn 6000rpm and at 125psi comp. thats nothing crazy. I get creative, If I dont use the gas for a while i run it in my dirtbike, lawnmower, weed wacker what ever i can find to burn it.
so 87 should have better response in this app. but try some and see if you can tell. also the higher altitude will benifit from a leaner mixture(87) and at that point the motor would have less compression so less need for the octane.

 

[adam98]

Re: fuel octane question for someone that knows

sorry i ment 89... but you are spliting hairs comparing 89 to 91. basiclly the same in my book. just buy the one that more people use because the other one has prob. been sitting in the stations tank longer...

 

[kbait]

Re: fuel octane question for someone that knows

Non-ethanol stores over time MUCH better... alcohol absorbs water, water is heavier than gas, fuel pick-up is on bottom of tank.. you get the picture.