unleaded vs premium leaded

[Seahorse]

what is best to use. i was wondering if better to use premium if boat sits for couple weeks. does normal unleaded break down with the lower octane level.

[Leo_N.]

Check the reccomendation in your outboard manual. Most recommend ULP 91 RON, which is standard unleaded. I don't think that premium actually has much if any benefit for a motor designed to run on standard.

[Thunderbird]

only the best PREMIUM!
I've found the motor won't die down in revs as much when there's a bit of swell.
could be my imagination running wild again but more octane=bigger bang. or i should say burn. correct me if i'm wrong!

[brentasauros]

yep...also..runs..cleaner..and..uses..less..klm/per..litre..
which..means..you.get..about..the..same.distance.. per..dollar..but..it's..better..for..power..and..f uel
economy...and..generally..better..for..your..motor .

that's..been..my..experience..anyway. ;)

[John_R]

I switched over to Premium on my Johnson 115 2 Stroke and noticed a significant increase in fuel economy - maybe 10%. This is great for going places like the banks where my 95 litre tank might be a bit small. I always carry at least another 20 litre jerry as well with a jiggle syphon on board for spill free fuel transfer.

The motor also seems to run a bit smoother.

Hey Gutterfish a new keyboard is about $15.

Regards


John

[billfisher]

John R,

Why don't you just carry a plastic fuel tank with fuel hose and connector? You don't have to muck around siphoning at sea and it can get you out of trouble if you have a water contaminated main fuel tank.
As to the original posting people have looked into this for racing purposes. It has been found that every engine has a sweet spot for octane rating where it runs best. The manuals usually recommend a minimum of 91 (ie unleaded). Certain engines may indeed run better with a slightly higher rating. Remember also the octane rating drops as the fuel ages.
Going a bit higher will not harm your engine. The higher ratings burn slower and will protect your engine from damaging knocking. If you go too high though it can lead to loss of power on two stroke engines due to their short duration of piston stroke combined with the slower burning leading to less 'push' on the piston. This more likely to happen with the really high octane racing fuels.
Another point is that some of the modern engines with computer management (as with some cars), continually monitor the octane rating of the fuel and adjust the timing accordingly.

[Seahorse]

thats all interesting fellas. i got 30 hp merc. think it wouls be ok.

[brentasauros]

yep positive :D

[bj]

I have just returned from a motoring holiday in WA. I have been using normal unleaded since the car was new & decided to go over to premium during the trip to see if there was any benefit. After around 2 thousand kays on the premium there was absolutely no benefit at all so for the rest of the trip stayed on normal unleaded.
I did the same thing in a tinny that I have with a 4/S 60 HP outboard. I started off with unleaded & then after 6 months or so went over to premium with a noticable improvement. I then went over to Shell Optimax a couple of years ago and the difference is better again much better. Why the improvement in the outboard motor & not the car I have no idea, but the motor runs beautifully & economical.

[Scalem]

Hi Seahorse,

I have recently done the whole comparison thing because my 2 stroke 70HP Jonno has been a proverbial pain in the butt every time I idled around crabbing or similar. I will in future always prefer premium if I plan to troll lures or crabbing because she oiled up so badly, opening up the throttle full did not clear it. However, the twirp who serviced it last put the wrong plug in it, but it definitely ran a little better on premium. I guess what I am trying to say is, if your motor was designed to use standard unleaded, and the fuel is not more than a few months old, you should not notice much difference unless there is something else wrong, such as wrong mixture ( too lean or too rich.) Or something stupid like wrong plug with lower operating temperatures. Stay with what the motor was designed for, provided everything else is OK.

Hope this helps.

Scalem

P.S I now replace my own plugs and tune it myself. Never ran better! Major services will still go into the workshop....

[Rod_Bender]

Premium all the way!!! Its only like where i live anyway, 4-6 cents dearer then the regular stuff. What's a few bucks to run better, go for longer trips and have it sound better. Highly suggest it in outboards. They suggest it for Yammy's.

[Leo_N.]

They suggest it for Yammy's.

Strange, I contacted Yamaha directly about this when I had my 50hp Yamaha 2-stroke. They said that they recommend standard unleaded and that higher octane ratings didn't burn any more efficiently in this outboard. I am waiting on a reply from Suzuki on whether it makes a difference for my new one.

[2iar]

Hi Leo,

Can you let us know the outcome when you get a reply from Suzuki.

Thanks,
Mike

[Leo_N.]

Sure

[New_fisher]

Rod Bender, can you let me know who told you this? I am curious as to which fuel to use as well in my 40 two stroke yammy and if we can find a firm source, then I will trial premium, Cheers Ray.

[QldKev]

Stay with the manufacturer recommendation for the octane. A couple of points higher is ok and can be a bit of insurance. It does depend on you exact engine; but without knock sensors etc the engine will not take any advantage of the higher octane; and can actually damage your engine. Octane is how much the fuel can be compressed before it spontaneously ignites; the side effect is it also has a slower burn. So with high-octane fuel in a standard engine with normal compression and standard timing; fuel can still be burning at a high velocity as it enters your exhaust chamber, which can cause damage; especially in 4 stroke engines as it can seriously damage a valve. Normally incomplete combustion will actually feel smoother as you are no generating peak power from the piston stroke. Some engines (better car engines for example) will actually adjust the timing to maximum for the given fuel; these often will benefit from higher-octane fuels. (Generally not from over 100 RON). If you have a rebuilt engine you would need to re-calculate the octane requirements.

PS. I do not work in the automotive, boating or fuel industries; this is based on my own research as I have been building my own performance car engines.

[Leo_N.]

Just had a chat with a Suzuki mechanic about fuel octane levels and his response was a definite affirmative for premium unleaded use. Much higher performance in the Suzuki 4-strokes and can leave for longer before the octane level goes down too low. He still thinks that 3-4 months is the most that you should leave it before adding octane booster. Apparently when you have old fuel in the tank, you can add octane booster and top up with new fuel with no worries. Saves siphoning to the car or wasting the fuel.

Cheers,
Leo

[billfisher]

Or just top up with fresh fuel. I don't re-fuel straight after a trip but do so just before I'm going out again.
Also most manufactures don't recommend an octane value. They just recommend a minimum. This implies you can go higher.

[johnnytheone]

I ran a tank full (300ltrs) of Prem. ULP in my 130 Evinrude for a couple of weeks of crayfishing, and the motor never started, idled, sounded or felt better. I never bothered to check fuel consumption, but I can't see why it wouldn't be better. I've found that was the case runing it in a car motor.

John

[falcon01]

I have just seen 100 octane shell optimax extreme which is 100ron but has 5% ethnol what would this go like

[Leo_N.]

I have just seen 100 octane shell optimax extreme which is 100ron but has 5% ethnol what would this go like

Probably similar to 95 RON. I am not too keen on putting ethanol in a car engine, let alone my outboard.

[Rod_Bender]

Hurlz

When i brought my 40 HP brand new in 2000 from my local dealer in townsville, they told me to use premium. I have noticed when i have ran the normal stuff it didn't run as smooth. I am having my motor serviced tonight, and i'll double check then. But i have been using it with my yammy since i brought it years ago, and i have never had one problem ever!!!

[Motorman]

Hey guys my 30hp Mariner runs better on Premium
as others have said idles and sounds better

Also with the Ethanol issue i wouldnt be keen using it as a few years ago Bogas were selling it with a warning on the pump not recomended for small engines i.e motorbikes, outboards, lawn mowers etc

Brad

[Rod_Bender]

Hurlz

Mate i checked with my mate last night when he serviced my yammy. He again agreed that premium is the only pretrol i should use. I have tried the BP Ultimate stuff, but at like 15-20 cents more expensive, i'll stick with the premium. Hope this helps.

[2iar]

Just had a chat with a Suzuki mechanic about fuel octane levels and his response was a definite affirmative for premium unleaded use. Much higher performance in the Suzuki 4-strokes and can leave for longer before the octane level goes down too low. He still thinks that 3-4 months is the most that you should leave it before adding octane booster. Apparently when you have old fuel in the tank, you can add octane booster and top up with new fuel with no worries. Saves siphoning to the car or wasting the fuel.

Cheers,
Leo


I've just had my Suzuki in for its' first service, and asked the mechanic his opinion. Same as Leo's bloke - Premium all the way, for efficiency, economy and power. I suppose I'll use it every time I fill up from now on instead of alternately.

Good luck,
Mike

[Angla]

Used BP Ultimate from day 1 in the 135 Optimax, 2003 model

The plugs were getting dirty (not fouling)

Mercury recommend 87 Octane minimum in the Handbook

Have gone back to Unleaded 92 Octane (nearly 8 months now)

No problems since and she runs like a charm with no noticable change.

Angla

[Mantaray]

now how do we sort out the good info here from the bad info and some of it is really (really) bad!

[New_fisher]

Rod Bender, thanks mate, I will check it out with my dealer and perhaps do the same,
Cheers Ray

[rowanda]

Hi guys
I work for BP , so rang their technical department on the subject
and was given the following
I'm not saying they are the best , I'm just saying this is their opinion
As I tell people, just make sure you use a major brand,as I know BP guarnetees
their fuel and will fix any probs due to fuel found faulty and I imagine all of the
majors have the same


Fuel News


Where petrol is kept for more than a week in a vehicle tank special considerations apply because that petrol will change with time. Examples are classic cars and bikes, veteran and vintage cars and bikes, racing cars and bikes, drag cars, boats, dual fuel vehicles etc.


HOW PETROL CHANGES
To understand what the potential implications are it is necessary to understand how petrol changes with time. In the fuel tank of a car exposed to the air the volatile components of the petrol will evaporate, these volatile components contain high octane compounds so the octane of the petrol will fall leading to pinging (knocking).

The volatile components have low density so as they evaporate the density of the remaining petrol increases, this will change the way the carburettor float sits so that the engine starts to run rich at all times, this will lead to overfuelling and carbon buildup. The remaining high density components have a high carbon content that promotes carbon fouling on spark plugs and they are hard to ignite so causing misfire, hesitation and stumbling. The petrol will oxidise in air forming gums that can clog jets, the sulphur compounds in the petrol will react with copper and brass components to form brown varnishes that clog the jets on the carburettors, affecting fuel air mixture and causing poor running.

The time that fuel takes to go off in a fuel tank depends upon the temperature, fuel and conditions, nominally it could take 1 week for octane loss to show, gum formation and sulphur attack is continual leading to a steady build up of gum and varnish.


HOW BP ULTIMATE HELPS
BP Ultimate has the following properties which help where vehicles are used only intermittently.

1) Low Sulphur –BP Ultimate has the lowest sulphur and this reduces attack on brass and copper components.
2) Metal Deactivator- BP Ultimate contains an additive called a metal deactivator that protects copper and brass components from corrosive attack.
3) Anti Oxidant – BP Ultimate contains an anti oxidant that protests the fuel and stops it oxidising and forming gums.
4) Corrosion Inhibitor – BP Ultimate contains a corrosion inhibitor that protects steel and iron surfaces from attack by water droplets and humidity.
5) Powerful Detergent – BP Ultimate contains a powerful detergent to keep inlet valves and fuel systems clean and remove build up of gums and varnishes.
6) High Octane – the 98 octane of BP Ultimate means that if octane is lost through evaporation of lighter components it does not reduce to the point where it can become a concern.


MAINTAINING FUEL IN VEHICLE TANKS
It is not possible to provide a foolproof strategy for vehicles that are used only intermittently, however the following principles help.

1) Always add at least a quarter tank of fresh fuel when the equipment is to be used when it has not been used for more than a week.
2) Always keep the tank half full to stop water vapour from being sucked in and condensing.
3) Use a high octane fuel.
4) Use a fuel that contains anti oxidants, metal deactivators and corrosion inhibitors to protect metal surfaces.

[Mantaray]

I know BP guarnetees their fuel and will fix any probs due to fuel found faulty and I imagine all of the majors have the same

haven't heard that one before, do you think they would fix engines if their fuel was lacking? now who was that fuel mob who killed all those diesel engines?


Where petrol is kept for more than a week in a vehicle tank special considerations apply because that petrol will change with time.

is there a difference being kept in a vehicle tank as opposed to other storage? fuel is probably older than a week before it hits the servo?

[Geoff_Atkinson]

Always use premium:

- It has a higher octane level so if your boat sits idle for a couple of month and the octane level deteriorates, the octane level will still be higher than that of regular unleaded would be.

- Read the other post on this page regarding ethanol. I always try to use Shell Optimax, a major reason is to negate the chance of putting ethanol in the tank. Any other premium would guarantee this as well.

I run a new 90HP Evinrude e-tec and have had trouble with stale fuel and/or water in the tank, which has now been remedied. I will never run anything but premium through the motor again as the performance and fuel economy using it has just been unbelievable.

Geoff