Octane Rating

[Firebolt]

http://www.maxrules.com/ Most posts within these forums recommend 87 Octane fuel for 2 cycle outboards. The site listed above also obtained from these forums warns against using low octane fuels. Once and for all: What would be recommended for use in a 1992 150 Evinrude carburated 2 cycle outboard??

 

[LubeDude]

Re: Octane Rating

Here is a quote from the site you posted.<br /><br />I use 87 octane in my car, why can't I use it in my outboard?<br /> <br />This stuffs' not fit to use in your lawn mower, let alone a $12,000 high performance outboard motor. The low octane and lack of detergent additives just leave you open to motor failures from detonation, gum and carbon formation, coked up rings and piston scuffing. Your automotive engine is a 4 stroke with totally different lubrication and fuel usage requirements.<br /><br />So what DO we all beleive, are the deturgent aditives the same (as we are led to beleive) in regular as they are in the higher priced spread or not, Supposidly by Stae laws they are. Maybe a mid octane would be better. I have always used 87 with no problems I know of, but??????????????

 

[oregonducker]

Re: Octane Rating

I'm getting more confused about octane. Most on this site are saying anything over 87 in most outboards (especially the older ones) is pointless and could even cause problems over time. I guess Max is talking about newer motors. Might make more of a difference there. <br /><br />And then we have the additive thing. Some say it's law that each grade has to have the same additives while I've also heard that each state is/can be different in that area.<br /><br />Then, my OMC manuals each say use a "minumum" of 87 octane. That leads me to believe that if 87 is the least recommended then more should be better. <br /><br />The arguements against higher octane on this site do sound reasonable so for now I'm going to stay with 87 . . . I think.

 

[JB]

Re: Octane Rating

Whoever wrote that material from maxrules is exaggerating hearsay.<br /><br />If a manufacturer tells you 87 octane unleaded (USA measurement, 91 by Euro and OZ measure) is okay to use it is okay to use. No manufacturer is going to allow you to use gas that will harm your engine. <br /><br />Many manufacturers recommend higher octane if available. That includes Suzuki in my DF70 4 stroke manual. I have been told that some 2 stroke manuals make the same recommendation.<br /><br />I used 87 in my Suzi with no problems until I realized that I would always have left over gas. I then switched to 91 or better SOLELY so I could use up the leftover in my truck, which requires 91 or better.

 

[quantumleap]

Re: Octane Rating

That article is more than a little misleading: <br /> <br /> 1. He states low octane contains no detergents or additives. All of the well known petroleum companies have SOME detergents in ALL grades of fuel. <br /><br /> 2. He then states that premium fuel contains too many octane additives that will gum up an outboard. This point is debatable.<br /><br /> 3. His recommendation is to use midgrade fuels most of which contain 10% alcohol, which within a short time absorbs mosture from the air. I have always been told NOT to use ethanol blended gas for 2 cycle engines. Water is the last thing you want to introduce into an outboards fuel supply!<br /><br />Do yourself a favor Firebolt, and follow the advice you get from the guys on this forum! There is a thousand times more combined outboard knowlege here than the advice you are reading on that site that was written from a single person.

 

[red10]

Re: Octane Rating

if you can get your hands on non-oxygenated gas, that would be the way to go, there is no additives like alcohol

 

[Dhadley]

Re: Octane Rating

1- Federal law now requires the same ammount of cleaners in all grades. There was a time that the cleaners were not in the low grade.<br /><br />2- High octane does contain oxygen bearing compounds so it can be rated as a higher octane. These compounds cause a hotter burn (leaner burn due to the oxygen in the compounds). That may well lead to coking. Especially if the motor is not set up right (lugging). Its all back to combustion temps.<br /><br />3- Water in fuel is seldom a good idea.

 

[RJS]

Re: Octane Rating

Higher Octane makes your engine run better is an urban legend. If you have no predetonation (pinging), you don't need a higher octane. The compression and tuning of the majority of the engines sold today require 87. I would rather spend the extra money on beer and bait.

 

[Dhadley]

Re: Octane Rating

RJS brings up a good point. We are talking about stock, recreational outboards. Not outboards that are "purpose built" and require high octane fuel.