Possibly the last word on octane levels for outboards.

[oregonducker]

I've been trying to follow this octane thing in these forums for several weeks now and have mostly been confused. It looks like those here who are the most adamant about what to use all say that anything more than 87 octane is pointless. Those people also seem to be very knowledgeable about outboards. <br /><br />The confusing thing to me is that most of the manufacturers say differently and pretty much every time a manufacturers recommendation has come up on this site for any reason, not just octane levels, the people who seem to know their stuff say, "Follow the manufacturers recommendation". I don't know about all motors of all vintages but here's what I've found. (Note the use of the word "minimum". Also note that the web sites quoted typically have more to say than what I've posted here. Trying to keep it as brief as possible.)<br /><br />1972 Johnson 25 hp service manual:<br />

Use leaded regular or leaded premium automotive gasoline.

I know we no longer have "leaded" but they do say "premium" is fine.<br /><br />1979 Evinrude 6 hp service manual:<br />

Use gasoline with a minimum pump posted octane number of 86.

Mercury web page:<br /><br />

Use a major brand of automotive unleaded gasoline with a minimum-posted octane rating of 87.

One poster on this site says that his Mercury manual and his dealer say to use 89.<br /><br />Bombardier (Johnson/Evinrude) <br />web page:<br />

Current recommendations are to use a minimum of 87 octane; 89 octane is preferred.

Nissan Marine<br />web page:<br />

The minimum octane rating that you should use is 87, however, we recommend using gas with an octane rating of 89 or higher.

Suzuki<br />web page:<br />

Low octane, stale or contaminated fuel simply doesn't burn as efficiently as fresh, high-grade gasoline.

I couldn't find or didn't want to take the time to download the Honda or Yamaha info. <br /><br />I'm thinking that this "more than 87 is pointless/bad" is simply not true and never was. One of those things that somebody said, that somebody heard, that somebody read, that somebody wrote... Or in the least it's applicable only to certain older outboards. The original manuals for my "older" outboards, while pretty specific on many points, don't seem to be too worried about octane levels as long as it's at least 87.<br /><br />I know some people here get pretty excited when someone says that something higher than 87 is fine so please don't jump on me. I'm just quoting the people who make these things. If there's a final say, they probably have it. Why would they say that octane levels higher than 87 are fine if they weren't? These companies have been making outboards for several years in the least and several decades in some cases so if their engineers are fine with higher than 87 octane fuels then what's the problem?

 

[ZmOz]

Re: Possibly the last word on octane levels for outboards.

I don't see what's so hard to understand. Use the lowest the manufacturer recommends. Anything more is a complete waste. All motors will run fine on higher than necessary octane. But there is no reason. There will be slightly higher carbon buildup with higher than necessary octane, but you should decarb regularly anyway so this won't be much of an issue. Also higher than necessary octane will actually reduce performance - there is less "gas" in 93 octane than there is in 87. Also keep in mind that octane ratings are different today than they were in the '70s.

 

[oregonducker]

Re: Possibly the last word on octane levels for outboards.

Why do the least when they say more is better? You'd spend possibly several thousand dollars on an outboard and then possibly take it several miles out to sea but use what is considered to be the least of anything in it?<br />What I don't understand is the contradiction between you, as well as others, and the manufacturers. If it's truly pointless and possibly harmful why do they all say 87 is the minimum and some say that 89 or more is preferred? They are all very specific about many things that go into their motors. Especially when the consumer has several options to chose from. TC-W3 rated engine oil for instance. And one is very specific about the fact that their outboards are engineered for petrolium based oils/lubricants so they recommend that synthetics not be used. But none of them are very specific about octane levels. Bombardier however, does say that higher than 89 is not necessary. On the other hand, Nissan says 87 is ok but 89 or more is preferred. If they aren't worried about it why should we be? I think this is the only topic I've seen on this site where manufacturers recommendations are directly contradicted so I guess that's why I'm pushing it.

 

[ZmOz]

Re: Possibly the last word on octane levels for outboards.

Use what the manufacturer says is best for the engine. If that's 89 then use 89. Most are 87. Using 93, for example, in a motor that is recommended to use 89 is completely pointless, and again, cost more and has less power.

 

[JB]

Re: Possibly the last word on octane levels for outboards.

The "Last Word"???<br /><br />HARharhar. . . **choke***. . .heheheheee!!<br /><br />Good one, Ducker

 

[Dhadley]

Re: Possibly the last word on octane levels for outboards.

The fuel changes every year. To understand whats happening in your motor now, simply install an EGT (pyrometer) gauge. Run different grades based on your particular engines requirements and see which runs coolest. <br /><br />It really is just that simple.

 

[oregonducker]

Re: Possibly the last word on octane levels for outboards.

JB,<br />Yeah, I know. I was wishing I could put a rolleyes smiley in the title. <br /><br />You know, there's a lot of info out there about octane. You can find stuff dating back to 1912. About the time I learned what a Dobbie-McInnes manograph was and had read about Highest Useful Compression Ratios I decided that I really didn't need to know more. I don't even remember what got me started. Is it legal to drink beer at 5:00 in the morning?

 

[JB]

Re: Possibly the last word on octane levels for outboards.

Hi, Ducker.<br /><br />To use all of the graemlins and alternate fonts, you need to click on the "Full Reply Form" link below the Quick Reply.<br /><br />Or, you can simply memorize the keyboard codes for the graemlins you want to use and enter the code in your Quick Reply. Simplest example is a colon, : and a close parinthesis ). Combine them and viola!, you have a smiley.<br /><br />Yes. It is always 5M somewhere, so 5:AM is Miller time. As I write this it is 5M in Dakar.

 

[Chinewalker]

Re: Possibly the last word on octane levels for outboards.

Oregonducker,<br /> I believe you're looking at the problem from the wrong side of it. 87 is often recommended as the minimum, because you don't want to go BELOW it. Anything above that won't hurt the motor, but won't benefit it either. A few years back there was some real problems with quality in 87 octane fuels and the mechs I know recommended using the 89 as it tended to burn cleaner with fewer deposits. The quality of 87 has stabilized now and there's nothing wrong with using it in a motor that recommends a minimum of 87 octane. Go above it if you wish, but you won't gain anything. Go below it at your own risk, as only then are you likely to create problems...<br />- Scott

 

[Cut n' Jump]

Re: Possibly the last word on octane levels for outboards.

Actually the higher octane fuels will perform the same as adding more oil.[not saying to do this] Less gas and the same air = leaner. Ya ever notice how 2 strokes get a burst of power right before they run out of gas? The difference in 87 - 93 octane wouldnt probably be noticable. I remember some vehicles a few years ago [Chevy trucks -I think] that would set off a check engine light if premium fuel was used! Run a 2 stroke too lean and it fries the rings and piston. Hey if 87 octane is cheaper why not use it? I tried bumping the timing a little at a time on my Johnson 70 and fillin up with 93 octane and didn't really notice a difference. Actually it started hesitating on takeoff before it felt any faster. If you haven't ever decarboned higher octane might get that last days use out of a motor clattering from spark knock. Seems like decarboning would be cheaper and safer than premium fuel.

 

[Oldsaltydog]

Re: Possibly the last word on octane levels for outboards.

After doing some reading and research on the subject, I have reached the same conlusion as you OREGONDUCKER. In my mind also, going a bit beyond the minimum octane requirement makes perfectly good sense.

 

[bundy]

Re: Possibly the last word on octane levels for outboards.

Which is better? 87 octane with no ethanol or 89 octane with 10% ethanol blend??

 

[quantumleap]

Re: Possibly the last word on octane levels for outboards.

According to ZmOz, The 89 octane is mixed from premium and 87 right at the pump, so 87 octane must be an ethanol blend too. Ain't that right Oz?

 

[JB]

Re: Possibly the last word on octane levels for outboards.

Ethanol blended gas is not universal. Gas formulae vary greatly with location and season.<br /><br />Some manufacturers say no to ethanol, others say 10-15% is okay. It depends on materials used in the fuel system.<br /><br />Check with the MFG. of your particular make and model.

 

[quantumleap]

Re: Possibly the last word on octane levels for outboards.

But JB, I'm confused because ZmOz said this and he said that it is a FACT:

First of all, ALL gas stations only have two grades, regular and premium. Mid grade is mixed right at the pump - that is a fact! Second of all, WHY would they only put it [alcohol] in the mid grade? That doesn't make any sense. It's there to reduce pollution, there fore they put it [alcohol] in the most used grade - 87. Some places (very few) do have non oxygenated PREMIUM, there fore the mid grade has less alchol because it is mixed with premium.

Are you saying that he is incorrect in assuming that this is the way fuels are forumlated and dispensed? And that ALL of the lower grade fuels aren't an alcohol blend? And therfore if midgrade is labeled as 10% ethanol, then regular must contain more alcohol?

 

[JB]

Re: Possibly the last word on octane levels for outboards.

ZmOz is correct within the narrow market he is describing.<br /><br />Here in W. Texas there is no ethanol in the gas and many stations offer regular and midgrade only.<br /><br />My point is that what is FACT one place is nonsense elsewhere. Even that changes with the season.

 

[ZmOz]

Re: Possibly the last word on octane levels for outboards.

Quantumleap, will you please stop "harrasing" my posts about fuel? <br /><br /><br />bundy - if you can find gas without ethanol, that is best; however, if it is "ethanol season" where you live that would be nearly impossible.

 

[quantumleap]

Re: Possibly the last word on octane levels for outboards.

Now that's original Oz. Where do you get your snappy comebacks??<br /><br />Oh, now I see that you bring up that the use of alcohol in fuels may change based on the season. Funny, JB just brought up that point in his post above. But I'm sure you already knew that. Didn't you.<br /><br />I always try to persuade people from following bad advice. Your most recent recommendation on the use of sugar contaminated fuel is a classic!

It certainly can't be good for it. I would pump it out, save it, and burn it a gallon at a time mixed with good gas.

Let me get this straight, it can't be good for it, but if you dilute sugar contaminated gas with new fuel, then it's ok???

 

[ZmOz]

Re: Possibly the last word on octane levels for outboards.

Originally posted by Quantumleap:<br /> Now that's original Oz. Where do you get your snappy comebacks??<br /><br />Oh, now I see that you bring up that the use of alcohol in fuels may change based on the season. Funny, JB just brought up that point in his post above. But I'm sure you already knew that. Didn't you.<br /><br />I always try to persuade people from following bad advice. Your most recent recommendation on the use of sugar contaminated fuel is a classic!

It certainly can't be good for it. I would pump it out, save it, and burn it a gallon at a time mixed with good gas.

Let me get this straight, it can't be good for it, but if you dilute sugar contaminated gas with new fuel, then it's ok???

EDIT! First of all, my name is zmoz, NOT "Oz". Yes, I know fuel is not allways oxygenated in most parts of the country. Some places have it in winter, some in summer, some year round. But nowhere has it in just 89 octane. That is just stupid. Tell me, since you're such a genious on the subject of fuels, why would they only oxygenate one of the least used fuels? The point of oxygenation is to reduce emissions - how much sense does it make to reduce emissions in only one grade of fuel, which is hardly used compared to 87? That would be like putting catylitic converters only on Honda Accords.<br /><br />And yes, I wouldn't have any problem using a small amount of the sugar fuel in my outboard mixed with alot of clean gas. As others have said, it doesn't mix with gas. The majority of the sugar will remain on the bottom of the tank. The tiny bit that would get into 1 gallon of gas mixed with 20 clean gallons isn't enough to throw a fit over. That's what fuel filters are for. If YOU don't want to use it, that's great. Dump it out, I don't care.<br /><br />Now stop. You're sounding silly again.

 

[quantumleap]

Re: Possibly the last word on octane levels for outboards.

Zmoz- I'm sorry, I didn't mean to upset you. But, by the way, you are wrong, again. I live in the state of Iowa, and here the ONLY grade of gasoline with 10% ethanol is midgrade 89 octane. Every station. Every town. Same choices. Only variant is some offer 91 octane premium and some offer 92 octane with no alcohol. None in the 87 octane either. UNDERSTAND? That is the point I have been trying making to you, and the point that JB touched on earlier. You are assuming that every thing is the same as in your corner of the world. It isn't and you should take that into consideration when making your posts.