Unleaded or Premium

[trout1105]

I have used both unleaded and premium in all my 2 stroke outboards without doing any damage and I found that the premium fuel was better than the unl3aded.
I now have my verry first 4 stroke outboard (115 Suzuki) and am wondering if I can still use 95/98 octane in this engine like I did on my previous 2 strokes.

[bsperka]

I have used both unleaded and premium in all my 2 stroke outboards without doing any damage and I found that the premium fuel was better than the unl3aded.
I now have my verry first 4 stroke outboard (115 Suzuki) and am wondering if I can still use 95/98 octane in this engine like I did on my previous 2 strokes.Of course you can. What do you expect higher octane to do to the engine that may be detrimental?

[trout1105]

Of course you can. What do you expect higher octane to do to the engine that may be detrimental?

I don't know, Thats why I asked.skied
The engine has only done 340hrs and I don't want to bugger it up.
I imagine that the higher octane fuel will make it run more efficiantly and maybe I could get more range out of a tank of fuel.
I currently get 1.2 to 1.5 miles per litre (depending on conditions) and wouldn't mind getting better than that with the 95/98 fuel.
I will run the tank super low and fill the boat up with premium ans see if there is any notable differance [thumbsupbig]

[Gordie]

I can't see it doing any harm, but to satisfy yourself, check it out in the user manual.

[trout1105]

It only says use unleaded fuel only, The 95/98 is premium UNLEADED as far as I am aware.

[PhilipA]

High Octane fuel does not give more economy unless the engine is tuned for 98 octane and there are knock sensors fitted.
I doubt that is the case for an outboard.

I suggest that you use the minimum octane specified by the manufacturer and maybe dose it with fuel preservative if you leave it a while with fuel in it.
That is with the proviso that you do not use E10 as the alcohol can deteriorate in a shortish time and attract water .

Most Japanese cars are designed to run on 91 and my Jazz loves it. The Jazz engine is an outboard engine. I would think that an outboard would be designed for the same. But if you like using 95 or 98 it will not harm anything.

Regards Philip A

[trout1105]

Every third tank full I add a "glurk" of metho to try and combat the moisture entering via the fuel vent, It seems to be working so far.
When I first got the boat I drained the tank and it had about 5l of water in it so I am a bit weary about moisture build up.
Here at King Ash Bay there is only a 8c differance between unleaded and premium so it wont cost much more to try it out.

[Dorian]

I have used both unleaded and premium in all my 2 stroke outboards without doing any damage and I found that the premium fuel was better than the unl3aded.
I now have my verry first 4 stroke outboard (115 Suzuki) and am wondering if I can still use 95/98 octane in this engine like I did on my previous 2 strokes.

The owners manual for my 70Hp Suzuki 4 Stroke, recommends 91 or 95 but suggests not to use 98 or Ethanol. No idea why not 98.
I don't get any noticeable mileage difference between the two but then again don't do really do any long repeat hauls to compare.
I think it runs slightly better on 95 than 91.

[Dorian]

Every third tank full I add a "glurk" of metho

You should really stop doing that as it's making your fuel into an ethanol fuel.
Add an external water trap / filter if you don't already have one.

Cheers Glen

[PhilipA]

I was trying to think of the name of the stuff I use in the mower fuel.

It is "Stabil" and you can get it a Supercheap.
Regards Philip A

[4bee]

I don't know, Thats why I asked.skied
The engine has only done 340hrs and I don't want to bugger it up.
I imagine that the higher octane fuel will make it run more efficiantly and maybe I could get more range out of a tank of fuel.
I currently get 1.2 to 1.5 miles per litre (depending on conditions) and wouldn't mind getting better than that with the 95/98 fuel.
I will run the tank super low and fill the boat up with premium ans see if there is any notable differance [thumbsupbig]


Isn't filling the boat up it a bit extreme as well as very dangerous. I mean, where would you sit? You'd really be better off filling the tank up I reckon.
[biggrin]

Oh, I see what you mean.[smilebigeye]

[bsperka]

I don't know, Thats why I asked.skied
The engine has only done 340hrs and I don't want to bugger it up.
I imagine that the higher octane fuel will make it run more efficiantly and maybe I could get more range out of a tank of fuel.
I currently get 1.2 to 1.5 miles per litre (depending on conditions) and wouldn't mind getting better than that with the 95/98 fuel.
I will run the tank super low and fill the boat up with premium ans see if there is any notable differance [thumbsupbig]From Wikipedia
"An octane rating, or octane number, is a standard measure of the performance of an engine or aviation fuel. The higher the octane number, the more compression the fuel can withstand before detonating (igniting)."
IIRC they have more mid-range volatiles that allow them to do this.
No extra energy in the fuel (of note), but having a higher compression ratio in the engine design means that more energy can be extracted for the same amount of fuel.
Modern petrol engines with direct injection overcome octane limitations and have a higher compression ratio than port injected engines through introducing the fuel at a later stage of compression.

[PhilipA]

I will run the tank super low and fill the boat up with premium ans see if there is any notable differance [thumbsupbig]
Of course you will detect a difference, smoother more powerful.
it's called the halo effect.

Regards Philip A

[Pedro_The_Swift]

so, what happened to the previous engine?
https://www.aulro.com/afvb/attachments/follow-me/142018d1530936356-finally-20180707_112536.jpg

[trout1105]

It's the same engine, 115 Suzuki 4 stroke.

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The main thing with a 2-stroke is to use a quality 2T oil, like Evinrude XD100. It is exxy, but more than worth it. Also a dash of Stabil with each new batch of fuel if it gets stored away.

[rick130]

A good two stroke oil will have calcium sulfonate as an additive to combat moisture and corrosion.
It should be listed, it's also used in racing two stroke oils to stop throttle sticking in slide carbies, and to prevent corrosion when not in use.

[Slunnie]

From Wikipedia
"An octane rating, or octane number, is a standard measure of the performance of an engine or aviation fuel. The higher the octane number, the more compression the fuel can withstand before detonating (igniting)."
IIRC they have more mid-range volatiles that allow them to do this.
No extra energy in the fuel (of note), but having a higher compression ratio in the engine design means that more energy can be extracted for the same amount of fuel.
Modern petrol engines with direct injection overcome octane limitations and have a higher compression ratio than port injected engines through introducing the fuel at a later stage of compression.

Thats it, its made from lighter fractions when refining. You can run more compression, more ignition advance and it will burn better at higher RPM - I don't think any of these will apply to the boat. The other thing to consider is that it is significantly more castnogenic in both the fuel and the emissions, and it is more important to keep the fuel cool and sealed so the lighter fractions don't vapourise out.

[trout1105]

I have tried the premium now and won't be using it again.
There was No noticable differance in performance or fuel economy and the engine tended to idle a little roughly using the 95 octane fuel.
Ah well if you dont try something you will never know.

[DiscoMick]

If it's tuned to run on unleaded then I doubt if there would be any advantage in using premium.
Not a two-stroke of course, but I haven't noticed any advantage in using premium in our Mazda 2 - it's perfectly happy on unleaded or E10 and no difference in performance or economy that I can notice.

[Collins]

I ran comparisons with both Standard & Premium fuel in a 200HP Suzuki fitted to a Hooker 6.7 WRC. In near identical conditions the WOT speed & fuel consumption was better with the Premium. Hoe shot performance was also noticeably improved. Over-all after the trial I continued to use premium fuel

[Eevo]

You can run more compression, more ignition advance and it will burn better at higher RPM - I don't think any of these will apply to the boat.

although you can run more compression, engines are static in their compression ratio. the more ignition advance is the main benefit, if the engine allows it.

i think they also burn cooler as the is less waste. not 100% sure on that though.

[TasD90]

We had a marine engine specialist at our fishing meeting the other night and his recommendation was just to use normal 91 octane petrol for all outboards.

Peter.

[DiscoMick]

I thought most Australian engines were tuned to accept 91, unless otherwise stated, so there was no advantage in going to a higher octane fuel.
It's not scientific, but I have experimented with our 1.5 litre Mazda 2 on 91, E10 94 and premium and I didn't notice any advantage from premium, either in performance or fuel economy. Not scientific, just real world, of course.

[PhilipA]

Just to clarify, if a motor is tuned for 98 octane eg say a Golf Gti the it will perform better on 98 than on 95 or 91.
AFAIK the main reason for this is that the ECU advance is tailored to 98 octane.

The knock sensors on most modern motors retard the ignition advance in stages if knock is detected as is the case with lower octane grades. Some people notice a rattle at first while accelerating with lower octane fuel , then nothing as the ECU retards the ignition advance.

If a car engine is tuned to 91 octane as with most "run of the mill" Japanese cars , then there is no advantage in running higher octane fuel , other that the effects of a lighter wallet.

European fuel standard is 95 octane , vs Japan and Australia at 91, so most "run of the mill" European cars will benefit a bit by using 95. Although seeing E10 is now advertised as 94 octane then the effect should be pretty minimal for 94vs 95.
If an outboard was tuned to 98 then it would be an advantage to use 98 , but I doubt very much whether outboards are tuned to 98 or that they have knock sensors. The Honda Jazz engine is tuned to 91 octane and it is the same engine as used in the Honda 115Hp? outboard.

Regards Philip A

[bsperka]

Wouldn't recommend running a car that requires 95 octane on a lower octane fuel.

[Slunnie]

although you can run more compression, engines are static in their compression ratio. the more ignition advance is the main benefit, if the engine allows it.

Not all engines are static in their compression ratio, although that one probably is. Hi octane is about ignition resistance, which is why increased compression ratios as the fuel will tolerate increased temperatures prior to flashing. A high compression motor is more efficient, however you may use that efficiency. The reason ignition spark is advanced is just because its harder to ignite and so it is advanced to where it is purely to make the engine run properly. The end result internally to the engine with regards to ignition timing is similar irrespective of what combination of octane and compression.