Originally Posted by printman71
I can only wonder.
I would suggest that octane is the most widely misunderstood subject in all of boating. Or actually in all of anything to do with a piston engine.
They certainly seem to be hypersensitive and more vocal about it on the forum that you mention. A lack of knowledge would be my guess.
Has the inner web been better or worse for educating people? Bad information gets printed, people believe it, and then they spread bad information further, believing it to be correct.
But maybe I am doing that now.
Is higher octane than recommended bad for the engine? I'm not going to do it, but would it damage a SHO to run racing grade (100+) octane.
It has always been my understanding for the 50 years I have been driving (and 20 for boating), that higher compression requires higher octane to keep from engine detonating.
Does higher octane burn hotter or cooler?
That might be the one thing that we can agree upon.
Well, maybe not.
Higher octane the slower it burns.
If it's designed for 87 then 89 is okay same if it's designed for 89 then 91 is okay. Just get it close and you should be okay.
My XB Calls for premium so I use 91 or 93 what ever Shell has.
Steve McQueen "Le Mans"
Own the Champ!Life Long Petty Fan!
2003 ChampioN 2006 250 Merc. XB, Prop By Mark C.
2002 Ranger Okeechobee Special EvinRude Ficht 90 / 9.9 4-Stroke GLAD to have a Get me to the Dock motor maybe!
The recommended rating with ethanol is better than a higher rating without
Better in what respect? For the motor, for the user, for the pocket book, for ???
If an engine maker recommends 87 minimum (or 87 or greater) is he not also recommending 89, 91, 93?
I won't get into a pissing match over octane, but if anyone wants a.good read go to sunocos site for their racing fuels and read away. Octane is only 1 factor with fuels resistance to detonation. The higher the octane the harder it is to light. BUT the actual burn after it lights can be controlled also. Everyone is worried about a few points to high but some are willing to take the risk of being on the edge of too low and that includes a old batch of fuel. It is not worth it to me for the VERY minimal hp loss if any of a point or two higher octane. Some of the folks at Sunoco are very informative on their fuels. They helped a ton a few years back with engine builds and fuel recommendations. Anyone like to guess what octane a 9k rpm Nascar runs on? How about some of the older 18+k rpm Indy car engines. The info is on Sunocos site. I was way wrong on the older Indy cars! Cj
Last edited by CJ1; 03-05-2019 at 08:23 PM.
2002 X19 200HP OX66 HO Vmax,HPDI lower, it lives, thanks Hydro Tec.
Is there any engine maker (Mercury, Honda, Tohatsu, Yamaha, Evinrude, Suzuki) that provides a caution or warning against the use of any octane grade that is above the minimum specified value? If so, I can't find anything from any of them.
If there was a concern about the use of gasoline with an octane rating that is above the minimum specified would it be reasonable to think at least one of them would say something about it? They go on and on about the negative aspects of ethanol. But I will be darned if I can find a word about too much octane.
Lots of innerweb stuff. Nothing from the engine makers. That I can find anyway.
Wish ethanol free was an option for us but it's not so we do our best with it. So far it hasn't been an issue for me.
Own the Champ!
2003 ChampioN 2006 250 Merc. XB, Prop By Mark C.
2002 Ranger Okeechobee Special EvinRude Ficht 90 / 9.9 4-Stroke GLAD to have a Get me to the Dock motor maybe!
Nope, nothing that I have found or experienced. I actually ran my lawnmower on 114 octane fuel just because I had it and love the smell, It still runs and seems to be no worse for wear. So I would love to see proof of the damage or excess carbon that some have stated. Ran a 11 to 1 big block a season on the same 114 fuel that I ran my 13.5 to 1 big block and the lower compression engine had 0 carbon in it and it saw quite a bit of street miles. 87 octane is less refined than 93 and only stays fresh for a couple of months and that's without ethanol. 93 will stay fresh for up to 9 months, Soooo what one would you rather have in your boat that may not be used for 3 months at a time? CJ
2002 X19 200HP OX66 HO Vmax,HPDI lower, it lives, thanks Hydro Tec.
If it burns slower what effect might that have on power output?
From what I understand.....the higher the octane rating of a fuel the higher the flash point it has. Not slower burning, it can just take higher compression/temperatures without pre-detonation which cases a loss of power and what is referred to as "spark knocking". Recommended octanes are derived from the compression that each type motor develops in order for the engine to run as efficient and powerful as possible. Recommended octanes do run better than the others!
Elwood....Bass Cat Strong
2020 Bass Cat Eyra
2020 Mercury 300R 4S (1E081080)
Hell Yeah!!!!!!!!
Sorry I brought it up....
Ever heard of pandora's box?
At least here on this forum we can stay civil while discussing it. On other forum's, not so much. If you disagree with the head kahuna you can be put in a pot and boiled. He does not take lightly to anyone offering a contrarian point to his way of thinking.
Don't be, best thing you could do. The truth is there sometimes you just need to dig for it! When in doubt I will just go to the manufacturer. Sunoco is responsible for literally hundreds of millions of dollars of engines and there tech line is great. They would not have the rep they have if they were guessing. Cj
2002 X19 200HP OX66 HO Vmax,HPDI lower, it lives, thanks Hydro Tec.
Where is jethro1 when we need him
I think he got banned for arguing with someone over on the Mercury board last year or the year before.Where is jethro1 when we need him
That's too bad he was a great source of Yamaha tech
Jethro1 helped me on more than one occasion. Miss his knowledge as well.
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