Stndard or super fuel pros and cons

[NEW HORIZONS]

I am considering switching to super fuel in my 40hp 2stroke yammy .any suggestions /thoughts welcome

new horizons

[TheRealAndy]

High octane fuels are for high compression engine. Use what the manufacturer recommends in the manual. IF the manual does not say to use higher octane fuels, you are better off sticking with regular unleaded as the turnover of the fuel is typically much higher

[Chimo]

A guy I trust told me a day ago that 98 goes off a lot quicker than 91.

I know the 91 I use seems to be fine even though sometimes it sits, as a full tank, for months at a time between uses. It always gets filled to the brim after use so very little air in the tank which might also help to minimize water take up from the air..

[TheRealPoMo]

My 4.3 Volvo diesels (runs on) on 91 so I use 98. Can be months between outings and it seems fine though I always top it off with 30 litres or so on the way out.

Sent from my SM-G900I using Tapatalk

[swof63]

My 4.3 Volvo diesels (runs on) on 91 so I use 98. Can be months between outings and it seems fine though I always top it off with 30 litres or so on the way out.

Sent from my SM-G900I using Tapatalk

I would be very reluctant to run diesels on either 91 or 98. I would stick to the recommended cetane rated diesel fuel. Compression ignition engines don't fare too well with petrol (although I think Mazda are working on hybrid spark/compression ignition petrol engines ).

Cheers



Sent from my iPhone using Ausfish mobile app (http://r.tapatalk.com/byo?rid=91595)

[RayLamp]

I've been told (and heard in a few separate places) that outboards don't require or utilise 98 to its potential. What I have also been told by someone in the industry is that the higher octane fuels keep better. Something to do with the quality controls etc required to manage 98...can't quite remember.

So I reckon its probably 6 of 1 and half a dozen of the other.

[552Evo]

I was told the same as RayLamp. When I picked up my new boat with a Merc 150 fourstroke I was told only use regular unleaded (91 octane). That was over a year ago, only done 100 hours on it though. But I will stick with regular. It's what the engines are designed for.


Sent from my iPad using Tapatalk

[TheRealPoMo]

I would be very reluctant to run diesels on either 91 or 98. I would stick to the recommended cetane rated diesel fuel. Compression ignition engines don't fare too well with petrol (although I think Mazda are working on hybrid spark/compression ignition petrol engines ).

Cheers



Sent from my iPhone using Ausfish mobile app (http://r.tapatalk.com/byo?rid=91595)Sorry poor wording on my part...it's not a diesel engine - "dieseling" in a petrol engine means it runs on after the ignition is off
Typically when the head and valves are carboned up which isn't the issue here - it just needs the higher octane fuel.

Sent from my SM-G900I using Tapatalk

[juggernaut]

I am considering switching to super fuel in my 40hp 2stroke yammy .any suggestions /thoughts welcome

new horizons

Given that oil reduces the octane rating of fuel - smart move.

I use BP 98 in everything I have, except for the cruiser which is Caltex 95 on-sold by Baileys Fuels at the dock because I have no other choice. I use Stabil storage in my 2 stroke fuel mixes and Starbrite Startron in the cruisers tanks (nearly 1,000 litres) which has eliminated all traces of water I used to see in my fuel filters when I wasn't using an additive.

[ericcs]

[QUOTE=juggernaut;1637446]Given that oil reduces the octane rating of fuel - smart move.

fair comment if he uses pre-mix, oil injection wouldn't be a problem!

[TheRealAndy]

Sorry poor wording on my part...it's not a diesel engine - "dieseling" in a petrol engine means it runs on after the ignition is off
Typically when the head and valves are carboned up which isn't the issue here - it just needs the higher octane fuel.

Sent from my SM-G900I using Tapatalk

Dieseling in low compression engines is usually a problem with high cylinder head temps. Maybe the cooling system needs attention?

[TheRealPoMo]

Dieseling in low compression engines is usually a problem with high cylinder head temps. Maybe the cooling system needs attention?Yep fair point Andy but I checked head temp with an IR sensor and no issues. Timings a possibility too but it runs well and I chucked my timing light years ago. I have read that people in the US have similar problems with low octane fuel on these truck engines.

Sent from my SM-G900I using Tapatalk

[scottar]

Maybe I am just lucky but in 30 years of boating running all sorts of two stroke engines - premix, old school oil injection and for the last 5 years an E-Tec, I have never experienced any sort of fuel issue running standard grade fuels - even with periods of lay up of 6 months without running any sort of additive. I don't bother topping off tanks after a day out - I refuel the day I am going but sometimes that isn't a lot of fresh fuel going in and at times engines are run on year old fuel on the hose at home. I can see the possible benefits with modern 4 strokes with variable valve timing though.

[tunaticer]

Curious as to how one would actually measure the difference between the fuels whilst on operation?
You can not go by miles per gallon as the weather significantly changes trip to trip.
You can not go by horsepower produced unless you can attach a dyno to it somehow.
You can not go by feel because that is not a guage with a benchmark.

You are simply asking for other peoples opinions whether their advice is right or wrong.

I suppose you could borescope the cylinder for cleanliness after running for a suitable distance on one fuel then check again after a similar distance on the other fuel and try to guage any differences.

FWIW i run regular unleaded on my old two banger and it has run well all of it's 22 years and maybe 5000 plus hours, again the hours there are subjective.

[TheRealPoMo]

Dunno about boats but 20 years or so of extensive testing on all sorts of bikes reveals an increased range of about 10% using 98. I still get arguments but am convinced. An extra 20km to a tank is noticeable when you have to fuel up every 200km or so.

Sent from my SM-G900I using Tapatalk

[GBC]

Can you get 91 octane fuel that is ethanol free? All the stuff in the city seems to have it. I have run 95 in boats for that reason alone for a long time.

[ericcs]

i use the yellow 91 shell bowser, no ethanol in that!

[TheRealPoMo]

I think it may have some ethanol in it. Up to 1% before they have to advise I have heard.


Sent from my SM-G900I using Tapatalk

[ericcs]

hmmm, i could be eating my words!

https://www.colesexpress.com.au/shell-fuels/shell-unleaded.aspx

[fishtragic]

I used 98 whenever possible and sometimes 95 if i had to in a hpdi and was still faultless when i sold it at 1400hrs, new 4stroke motor was recommended to use 91 by the manufacturers website and now im told by the dealer to use 95. Bottom line is the higher octane fuels are cleaner an more bang for buck in my limited knowledge of fuel science.

[billfisher]

The first reply was closest to the mark, ie low compression engines (ie outboards) will not perform better with high octane fuels. Though there is one proviso in that different chemical bonds have different energy content so it is possible if the fuel is a blend which has a higher energy content then your outboard will perform better. Maybe give premium a try and see if you notice a difference.

[TheRealAndy]

limited knowledge of fuel science.

At least that part is accurate.

[stevej]

higher octane ratings allow you to advance ignition more for more hp
in my classic car on 91 I can run 8 degrees of advance, I just replaced the engine with a new race spec engine and am now running 98 I can run 12-13 degrees of advance.

unless the outboard can detect fuel type and adjust ignition you are gaining nothing performance wise
you will gain more detergents which can be detrimental to 2 stroke oil in kart engines we had issues with full mineral oils breaking down at 18,000 rpm

some use ethanol to boost octane racing but with a decreased energy rating hence you burn more for the same distance, some use other volatiles which if left for a few weeks in a boat tanks thats vented to the atmosphere will just evaporate off and your back to 91 or worse

people can believe what they want but 91 with no ethanol would be what I would use for any outboard rated to run 91 as per the manual

[juggernaut]

Couple of interesting articles I came across on the topic

https://www.tradeboats.com.au/trailerboat-news/features/1004/fuel-still-aint-fuel

and updated

https://www.tradeboats.com.au/trailerboat-news/features/1501/nulon-oil-review-does-it-perform-in-two-stroke-outboard-motors

[up the creek]

maybe scottar has never had a problem as it works just fine in little engines, which brings me to my point, racing or drag cars use high octane fuel and guess what they rebuild them all the time not just from high speed and revs but the fuel burns hotter in high octane fuels , so you have to ask yourself, does most smaller outboards need high octane fuel??? i believe in my opinion 91 is just fine and safer for small engines..



Maybe I am just lucky but in 30 years of boating running all sorts of two stroke engines - premix, old school oil injection and for the last 5 years an E-Tec, I have never experienced any sort of fuel issue running standard grade fuels - even with periods of lay up of 6 months without running any sort of additive. I don't bother topping off tanks after a day out - I refuel the day I am going but sometimes that isn't a lot of fresh fuel going in and at times engines are run on year old fuel on the hose at home. I can see the possible benefits with modern 4 strokes with variable valve timing though.

[stevej]

race drag cars run hotter cause they run them lean and advance timing for max hp
well beyond what's normal in a road car, speed costs money and they are prepared to pay the expense to win

so they rebuild engines cause they want to to win not because of fuel

[Heliduck]

The Octane rating for fuel does not designate calorific value, it designates the resistance to detonation. The higher the octane rating the higher is the fuels resistance to detonation when vaporized, that's why it is used in high performance engines which have high compression ratios & advanced spark timing.
As previously mentioned, the manufacturer does a lot of research on suitable fuel types & they want to advertise their product as the best for fuel economy & emissions so I'd suggest their recommendation would give you the best results for an unmodified engine.

[up the creek]

spose 1 way of puttin it,,, u most dont need 98 for ur lawnmower and 91 fuel is still fuel it works.. all the clever marketing tells you to use 95 or 98 as it does this and that,, and yes it adds a little more power to high performance engines. so one way maybe of putting it is.... smaller outboards 30hp and under 91 will be, well sufficent. if you want more hp get a bigger engine 98 aint gonna make a 2-30hp a speed boat.. but i believe no matter what anyone says. a little engine running cool is vital and higher burning fuel can get ur motor hotter and they dont like that.. as scottar said hes always run 91 and no problems.. i dont think a few drops less fuel or 4% hp gain is worth heating little motors up...

[Jason Green]

Just my two cents worth the last few trips I have been running 91 instead of 95 or 98 and my Yamaha gauge is telling me my motor has gone from a average of 2.2 km to the litre to 2.4 at 4000 rpm so now I can go faster and still get my average consumption that I like to work a trip out on


Sent from my iPhone using Ausfish forums

[up the creek]

no doubt you will save fuel on 98,, is it a bigger hp engine? ... i got a 12l tank on mine lol so in my case i might not save much..

[swof63]

I think he’s saying he’s getting better mileage on 91.


Sent from my iPad using Ausfish forums

[Jason Green]

No I saved fuel on 91 not premium it’s a 115 Yamaha nearly 10 months old pushing 200 hours


Sent from my iPhone using Ausfish forums

[up the creek]

No I saved fuel on 91 not premium it’s a 115 Yamaha nearly 10 months old pushing 200 hours


Sent from my iPhone using Ausfish forums

well there u go.. ive never extensively tested it.. of course all we have to go on is the fuel companys pushing it on us.. maybe in some cases some and i say some people get more on 98.. but thats awesome u get better fuel economy on 91.. as said i dont know enough to tell someone theres no benefit of 98.. but for the bloody price lol i am happy with the performance and cost of my 91 which i use on my car mower and boat.. and all my engines last a long time..

[juggernaut]

The benefit of higher octane fuel is its resistance to knock and ping nothing more, nothing less. My new 8hp yami 2 stroke manual says to use a min of 90 and if knocking and pinging occurs to use a different make of fuel or higher octane fuel.

The links I posted on the previous page also highlighted that synthetic fortified oils fall out of suspension when used premix in 91 octane fuels, but apparently no so with 95. No problem though if you don't use synthetic or synthetic blend 2 stroke oils.

And in relation to a previous comment - I'm not so sure drag cars run lean mixtures - top fuellers are on the verge of hydraulicing they run that much fuel through the engine.

[shakey55]

There are many who run 91 and there are many who run 98 and everyone has some good and bad results.

I personally have a 2000 Model 115hp Johnson Oceanpro (2 stroke) and very happy with the use of 95.

There is mounds of literature for and against different fuels in different size outboards. I guess it’s what makes you happy that counts. Each to their own.


Sent from my iPad using Ausfish forums

[up the creek]

There are many who run 91 and there are many who run 98 and everyone has some good and bad results.

I personally have a 2000 Model 115hp Johnson Oceanpro (2 stroke) and very happy with the use of 95.

There is mounds of literature for and against different fuels in different size outboards. I guess it’s what makes you happy that counts. Each to their own.





Sent from my iPad using Ausfish forums


thats it shakey use what makes you happy in life and if others dont agree/like it well just do it your way.. dont verbally beat some1 up,, if i had a bigger hp engine like you id use 95,, as for me a run a 9.9 so me 91 does the trick just sweet.... :P

[up the creek]

The benefit of higher octane fuel is its resistance to knock and ping nothing more, nothing less. My new 8hp yami 2 stroke manual says to use a min of 90 and if knocking and pinging occurs to use a different make of fuel or higher octane fuel.

The links I posted on the previous page also highlighted that synthetic fortified oils fall out of suspension when used premix in 91 octane fuels, but apparently no so with 95. No problem though if you don't use synthetic or synthetic blend 2 stroke oils.

And in relation to a previous comment - I'm not so sure drag cars run lean mixtures - top fuellers are on the verge of hydraulicing they run that much fuel through the engine.


just a thought and could be wrong... but yamaha use 100/1 mix tohatsu and mecury 50/1 ... i dont care what motor i run i always go 50/1 (back of hippies or ill turn ya power off if i cant have me 50/1 lol) so the point is just cos yammie says there engine can handle 100/1 ive always run smaller engines on no less then 50/1.. maybe if its knocking and pinging uping the 50/1 mix may help... as said could be wrong but my motors on 91octane and 50/1 have never knocked or pinged,, just a thought to throw into the mix.

[stevej]

98 over 91 is 15-20% more here in the bush you are not going to save that same percentage in fuel use between the two

98 has cleaning detergents added its probably just giving a dirty engine and carb a clean

[stevej]

too small a sample size
could have just been other factors on the day
bimini up and down
wind behind you
flat surface v small ripples

[Jason Green]

too small a sample size
could have just been other factors on the day
bimini up and down
wind behind you
flat surface v small ripples

Hi stevej if you’re talking about my comment conditions have been the same as usual if not worse on the last few trips I have done and it’s still saying my fuel economy is running better on 91 I don’t know why but anyway it is
Usual day trip is 150-200 km
Roof doesn’t change bit hard folding it down and driving
Weight is usual except the last couple of trips heading out into 10-15 knot northlies with 4 foot swells at 4 seconds on a outgoing tide which is not real comfortable at the top end of Hervey Bay but I have been locking the ballast tank off keeping 150litres of water on for extra weight for the trip out which makes a big difference in comfort but does burn the fuel
I don’t know why it is doing better but anyway it’s saving me a bit on fuel money for more beer
When I get decent conditions to open her up next I guess I will be able to see whether there are any changes at wot


Sent from my iPhone using Ausfish mobile app (http://r.tapatalk.com/byo?rid=91595)

[stevej]

Jason wasn't aware of the large trips you were doing, any dollar saved is a bonus

[fishtragic]

At least that part is accurate.
I haven't checked in for a while so I just noticed the critique of my post.Thanks for confirming my admission of limited fuel science knowledge and possibly you could clear up all the other inaccuracies in my post for me so that next time someone asks for thoughts I won't make the same mistakes.

[Andy56]

this is my experience. Putting 98 instead of 91 does no harm to motor. Putting 98 in costs more, gives a slight boost to the performance does increas range slightly. No where near 10% improvements. On a cost basis, pay more go further, its a zero sum gain. Now if your motor is tuned to run 98, you would be crazy not to take advantage and. 10% gain has been factored in by design. Does 98 go off faster than 91? No idea but i have never experienced bad fuel either.
my take is that its just not worth it long term. Short term, hey it doesnt hurt and may clean up the insides a bit.

[TheRealPoMo]

this is my experience. Putting 98 instead of 91 does no harm to motor. Putting 98 in costs more, gives a slight boost to the performance does increas range slightly. No where near 10% improvements. On a cost basis, pay more go further, its a zero sum gain. Now if your motor is tuned to run 98, you would be crazy not to take advantage and. 10% gain has been factored in by design. Does 98 go off faster than 91? No idea but i have never experienced bad fuel either.
my take is that its just not worth it long term. Short term, hey it doesnt hurt and may clean up the insides a bit.Agree.
I reckon I got around 10% more range on every modern motorcycle I have owned and done the standard commute day after day. The XR had something like a 9 litre tank so I really noticed it there. Boats - dunno...probs not.

Sent from my SM-G900I using Tapatalk

[Dignity]

The higher octane fuels are more refined and have more stable hydrocarbons resulting in the ability to reduce octane loss and vapor pressure loss over a longer period of time. There is one answer to this conundrum, if you use your boat frequently 91 is OK, but if stored for any period then a higher octane would be preferable. Most motors benefit from going up to the next octane level but generally no further and would be considered a waste of money. There is also other factors involved but it starts to get complicated especially if you start comparing carby 2 strokes vs 4 strokes and even newer 4 strokes vs some old ones.

Best way is to test for your selves and be happy with your decision. I know of people where the pennies are tight and will always go the cheapest (except E10) and that is fine with me, others have done some research and have their opinion, fine with me also. I use 95 after talking with mechanics, both car and outboard, a mate who works in the fuel industry and another who is an industrial chemist so I am happy with my decision. ☺

[Cape Crusader]

G'day
Far from an expert but what I've read says higher octane is less volatile (less power in my mind)
I saw test of additives that raise the octane level in a racing team lab, power went down with increased octane
If you leave fuel sitting around, particularly in a ventilated container the light more volatile components evaporate and the fuel starts to degrade and the octane level goes higher
Higher octane is for high compression engines that may suffer pre ignition from using more volatile (explosive fuel)
I use a simple approach, just use what is recommended by the engine company
Cheers
Rod

[Jason Green]

I know this is 11 years old but it is worth a read
https://www.saltwatersportsman.com/boats/boat-maintenance/all-about-outboard-gasoline


Sent from my iPhone using Ausfish forums