Unleaded or Premium

[majed1965]

Hi All.

I am using unleaded fuel 50:1 mixture. I have 2 different views from 2 marine mechanics. One says to use unleaded only as premium has high octane and the other says only use premium. What is best to use on a 1977 70HP Evinrude? Thanks.

[John_R]

This subject has been done many times before and is controversial. The answer you gets depends on who you talk to.

I have a 2003 Johnson 115 carby two stroke with a 95l underfloor tank and only use premium for the following reasons:

1. Motor seems to run smoother and get better fuel economy. It is hard to measure economy because it varies with sea conditions.
2. Less chance of fuel losing enough octane from sitting for a few weeks to cause an issue.

I always store the boat with around half a tank and then top up with fresh fuel just before a trip. This also helps avoid getting water in the tank because the fuel vapour creates a positive pressure and keeps damp air out.

Hope this helps

Regards


John

[Marlin_Mike]

2003 Mariner 75HP 2 Stroke, I use normal unleaded, fill up night before each trip. Never had problems

Mike

[Kerry]

Regular unleaded, there is simply no reason or need to use premium.

Regards, Kerry.

[Black_Rat]

Regular unleaded, there is simply no reason or need to use premium.

Regards, Kerry.

Kerry,

I only use regular unleaded and have thought about using premium. Surley it would give you better performance because of the octane rating but not necessarily better fuel economey and the claims that they have additives to "clean" the fuel delivery system :-/

[Grunter71]

I thought the high octane/premium fuel actually went off quicker than regular unleaded. Not sure where I read this to back up the claim though.

[Hamish73]

I pretty new to this game, but have been playing with bikes (2 and 4 strokes) for years. As a rule of thumb, a engine will perform at it's best on the lowest octane rating it can stand withstand without pinging. Boat motors seems to have a low specific power output per cc, so one would assume they ther\y arent highly strung beasts that would require premium fuel. Especially in the case if a 1977 engine. They didnt even have premium fuel back then as far as I am aware.

[Kleyny]

i use normal unleaded in my 04 60hp 2 stroke.
Hamish they most probably didn't have premium back then but the leaded fuel of that era had a rating the same as the premium now (around 96)
some premium fuels don't go very well in carbied small motors. they are designed for injected motors.

if it was mine I'd run normal unleaded.

my 2c's

neil

[Astro]

So what would be the ideal fuel for a 2006 four stroke engine? Marine shop told my old man to use normal unleaded, but being an electronic fuel injected engine, wouldnt premium be a better option for a newer electronic injectred engine, it would run smoother and last longer because of the cleaner and higher ron fuel?

[Bin455]

Im in the NT and have just got a new 4.55m boat with a 50 hp Honda.
The dealer has told me that beacuse of the hotter weather up here regular unleaded goes off quicker and the fuel up here is basicly "crap".
He recommended that I use Premium Unleaded as it has a longer life when sitting in the tank and also told that buy useing Premium there was less chance of the fuel in the carbies "gumming up" if it was a long time between trips.
As its a new boat I dont think I will worry about that for a while as Im planning on doing a lot of fishing!!!!;D
I have aslo been told that by using Premium you get better economy and its better on your engine, having said that im on my third tank of fuel in my boat and Im only useing Regular unleaded. I do plan on useing Premium unleaded after this tank is gone just to see if there is any noticable difference.

But like someone said before you get a different answer when talking to different people.

[Seahorse]

this is a very important issue. one hears use normal unleaded. i tend to lean towards same theory as john r. I thought the higher the octane the better it was if left sit for couple of weeks. surely we have some experts on here to tell the truth about fuels, rather than everyone guess or go on hearsay. I certainly would love to know.

cheers
greg

[pacemaker]

I have been involved with high performance rally engines and have built many over the last 8 years. Hi octane fuel (PULP) I find usually begins to lose its performance after around 1 week. We have to run it in my engines as they all have a high compression ratio ranging from 10:1 to around 11.5:1 as well as some turbo applications and superchargers.
We drain the fuel out of tanks after every event. You can notice the difference between old PULP and new from the pump straight away. If the fuel system is a sealed system it will last a bit longer. Its my understanding though that most marine fuel tanks are of the non sealed type. I have used ULP on my 81 140 rude ever since I bought it and it preforms very well.
The other thing to remember here is the solvents used in PULP (optimax especially) to 1 increase the octane level and 2 to clean the fuel system, valves and bores (because of the higher combustion temps you will get more carbon build up at slow revs) These solvents in my mind should not be going anywhere near a 2 stroke considering the oil and fuel mix is the engines only anti friction defence(especially any fuel with ethanol added which could up the water content in the fuel). That's the way is see it anyway....:)

[Dignity]

Having a 200 litre tank - not sure I want to start mixing different fuels - use ULP as that is what the japs have been using for the last 20 years. In petrol, higher octane means slower ignition rates which avoids pingning especially in older cars. Does that mean it will go off quicker, I don't know. In my case how does one check with a large fuel tank, could try with a smaller tank, but having been through some recent expense on the old 150hp don't want tempt fate and all indications are not to use the Premium.

[Roughasguts]

Pacemaker, why don't you use Avgas in your motors, that be 100/130 octane, runs real nice in a car.

I hear you regarding Pulp and carbon build up, it also eats the older plastic parts and rubber in older models.

All those cleaners in the pulp can't be good for washing the oil of the crank and bore aswell. And may even break down the oil in a pre mix.
But yes I have used it in me outboard, it ran marginaly better.

But the only time I use it now is purely to clean me injectors in me car or a bit more Oooomph in me gutless Paj, for driving on sand.

The jury is still out for me, but I'm leaning towards Pulp shortening the life of your motor, due to the added solvents used as a cheap filler and octane booster.

[pacemaker]

Avgas is great but is banned in many events now (high lead content) and you have to have the car loged with a fuel passport to buy the stuff. And it is expensive. Smells good though. We get great results with PULP.

[Mick King]

Picked up my mates new boat on Saturday and the question was ask of the mechanic premium or unleaded mechanics reply normal pump fuel not sure of reason why. Mate has always used premium in everything he has owned so he thought it was needed. Mick King

[Roughasguts]

Yes Avgas does have lead, even though they say it's low lead.
But I guess if you can't use it, then Bummer.

If your in to experimenting with fuel try camphor balls or moth balls soaked until they disolve.

You get quite interesting results from that, but for the regular punter don't try it, unless your in to rebuilding motors.

[Dirtysanchez]

It is an interesting thread, and a lot of concern about how long the fuel stays in tanks, which is valid by the looks of things.. Can I please ask, how does this differ from the time the fuel spends in the tanks at the servo, or at the oil company ?

Is it just that it is fresher coming from the supply, or is it because you generally have a greater volume in the servo tanks etc ?

[roydsy]

It is an interesting thread, and a lot of concern about how long the fuel stays in tanks, which is valid by the looks of things.. Can I please ask, how does this differ from the time the fuel spends in the tanks at the servo, or at the oil company ?

Is it just that it is fresher coming from the supply, or is it because you generally have a greater volume in the servo tanks etc ?

Having worked in a large servo for quite a few years, i can tell you the fuel doesn't stay in the tanks very long. We used to sell or empty the tanks at least twice a week, sometimes 3 times depending on seasonal fuel sales. In comparison to some people who don't get out in their boat more than 3 or 4 times a year there is big concern for fuel tanks containing water.

The time the fuel sits in storage prior to this I have no idea.

I always use regular unleaded in my new 115 HP 4 stroke merc.

[FNQCairns]

I will use only unleaded in my 89, 90hp engine because it needs nothing more any increase in octane will go straight out the exhaust also the additives needed to control the artificial way they increased the octane rating are not considered best for use in a 2 stroke.

I will occasionally top up with premuim (like 1/3 max) to make myself feel better if the tank fuel may be a little old but still young enough to use, although I will never use undiluted premium by choice.

cheers fnq

[whiteman]

Doesn't anyone read their factory motor manuals? Both my Yammy 2s and Suzie 4s manuals specifically insist on ULP. No point paying a premium for a fuel that is not recommended by the manufacturer. Claiming "better economy" using PULP in an outboard is an urban myth.

As for "old fuel", I'm much more concerned about buying dirty fuel. Top up with new stuff regularly and have a quality fuel filter.

[Hamish73]

according to the BP website (and shell I think) they say their fuels are good for at least 3 months storage. I wouldnt be keen to test this theory on the water.

[BilgeBoy]

Once upon a time we used a fuel called STANDARD in all two strokes. Makes you wonder doesn't it!! It was no good because the lead in it...the lubricant...made you DUMB :P

Now we have unleaded....which they say is carsenojenic :-/

As Simon Towsend would say "The world really is wondeful"

BilgeBoy

[stark]

I understand two stroke mix oil/fuel effects the octane rating of the fuel. Why bother going to PULP in a two stroke? Even the oil injected type 2s would have the octane rating change due to the oil.

Many of the VMRs/Coast Guard run PULP in their 4s Outboards. I think this is more of the case of getting that marginal difference in performance for tight situations.

Other than the above, for my own preference I run ULP. It is as recommended and works satisfactorily (91 octane).

Just keep the fuel fresh. Found out the hard way with old fuel.

Cheers
John

[Roughasguts]

Once upon a time we used a fuel called STANDARD in all two strokes. Makes you wonder doesn't it!! It was no good because the lead in it...the lubricant...made you DUMB :P

Now we have unleaded....which they say is carsenojenic :-/

As Simon Towsend would say "The world really is wondeful"

BilgeBoy

Does make you wonder, a vehicle running ULP must have a catalytic converter or hot box in the exhaust. Ain't no outboard I know has one, and it couldn't with water going through it.

[littlejim]

if you look up what the experts say on octane there are a couple of things of interest in what they say.

One is that for fuel to be 'high octane' it has to be harder to burn/explode. That's so you dont get it going bang before it should. If you use it (HO) in an engine designed for lower octane fuel you aren't going to get more power, but there is a distinct possibility that you may get less power because it hasn't burnt properly by the time the exhaust port opens.

The other one is that they point out that the high compression engine's extra power doesn't come from the high octane fuel. It comes from the higher compression. The 10:1 engine behaves like it has squeezed 10 units of mixture into the space of 1, the 8:1 as though it squeezed 8 units into 1. The high octane fuel just lets you squeeze 10 into 1 without pre-igniting from the heat before the plug fires.

To me using the fuel the engine maker says in its book that it designed the donk to use makes sense and you don't waste a lot of money buying a more expensive fuel that gives you no return for the extra cost.

[Roughasguts]

Little Jim has a point LPG the gas you put in your car has a Higher Octane rating than PULP around 120 plus Octane rating. But to get any benefit from that fuel you need to run 20.1 but I guess we use it cause it's cheaper. And probably a better alternative to ethanol.

[krazyfisher]

so what if you can only get fuel at a BP its either ethanol or pulp?
thats my choice early in the morning. I go with the pulp

[Kerry]

Ethanol or PULP? Gee they don't give you much options. That makes life very difficult.

Ethanol is going to be a whole new nightmare for boats all by itself without any of the octane issues.

[krazyfisher]

is there much differance between 91 and 95

[Kerry]

Lets put it this way there is absolutely no way I would be putting BP91 (e10) in a boat. If the only other option is 95 and no other choice then 95 it would be but would be kicking and screaming. Gee Mackay is a bugga of a place for the number of BP E10 outlets?

[krazyfisher]

yep BP has removed unleaded and replaced it with e10 in mackay so its 95 or an extra 20-30min to fuel up

[FNQCairns]

Krazyfisher that's a shocker, what about taking a few 20L drums that will seal properly for use later, although you will need to pump it into the boat, might halve the trips. Under no circumstances would I use the e10 in an outboard engine!

E10 is so environmentally unfriendly when viewed in context of the 'whole' needed to produce it and get it to the pump not to mention the extra cost in using it over normal unleaded, the stuff gets such poor economy.

Environmental propaganda, Government and big business! We are in for an unnecessary and rocky next 10 years, in 20 with luck many will see the length and breadth of the shaft and actively set about extracting it :)

cheers fnq

[Scalem]

If I was planning a trolling trip for Macs with my 70HP 2S Jonno I would definitely use Premium in the hope she won't oil up as easily - But I don't have any facts to substantiate this, it's just a "Peace Of Mind" thing.http://www.ausfish.com.au/vforum/images/icons/icon11.gif

Scalem

[Kerry]

If I was planning a trolling trip for Macs with my 70HP 2S Jonno I would definitely use Premium in the hope she won't oil up as easily - But I don't have any facts to substantiate this, it's just a "Peace Of Mind" thing.http://www.ausfish.com.au/vforum/images/icons/icon11.gif

Scalem

"Peace of mind"? So it's only a feel good thing then without knowing one way or the other?

Why do people spend thousands of $$$$'s on an outboard then risk it all based on nothing more than "Peace of mind" ?? without the facts!

[PADDLES]

it's been covered before on here, but don't be confused by thinking that a higher RON makes the fuel burn hotter. little jim is bang on the money, the higher octane actually lets the fuel burn slower in a more controlled manner. this should kill the "oiling up" myth. also don't be confused into thinking that 2s and 4s engines have the same fuel requirements.

2s and 4s engines work on different principles. in a standard 2s the plug fires the fuel/air charge which shoots the piston downwards to expose the exhaust port and then the gas leaves via this port into the exhaust pipe. how quickly the burn happens is critical to how well a 2s performs so why would you want to make the flame front go slower and risk some of that fuel not burning until after the port is exposed and therefore lose all the energy from it.

in a 4s engine the fire can burn heaps longer because the piston can go all the way to bottom dead centre before it's work is done and then it gets forced out on the upwards (exhaust) stroke through the exhaust port/valve.

the reason you would want to make fuel harder to burn is to control it when you modify an engine. you can make more power by advancing the ignition and/or raising the compression. this applies for both 2s and 4s engines. a modern engine management system will work out how far the timing can be advanced without knocking/pinging/preignition occuring (most of the fire happenning before the piston hits top dead centre) so most modern 4s engines with all the variable timing and valve setups and relatively high compression will work better with pulp. for a standard 4s tuned normally and a conventional 2s however (as long as it hasn't got a modified squish) the standard unleaded should work best and most efficiently.

[Kerry]

Some might be missing the real/main issues with E10 as in a marine environment it would appear there is no differentiation between engine technologies, it is all marine craft and marine engines.

BP actually states that Ethanol is NOT SUITABLE and NOT to be used in general aviation aircraft, ultralight aircraft or marine craft. Is is not recommended for motorcycles with fibreglass tanks or steel tanks repaired with epoxy materials. Ethanol blends are affected by water and should not be used in marine engines. Currently BP does not recommend Ethanol blends for use in high speed two stroke applications where oil to fuel ratio is critical.



Regards, Kerry.

[krazyfisher]

FNQ
great idea but average between 80-100l per trip thats a lot of fuel cans sitting around

[newchum]

FNQ
great idea but average between 80-100l per trip thats a lot of fuel cans sitting around
krazyfisher, i use a 44gallon drum and hand pump i live out of town and use up to 200lts per trip, saves towing a 7metre boat into a servo and painfully filling up when it's out of my way

[PADDLES]

hey rodney, how do you transport the drum around? i've been thinking about doing the same thing as you with the 44.

our local servo only sells phillipines unleaded or an e10 mix of phillipines unleaded either way i'm figuring it's already quite a few weeks old by the time i buy it.

so was thinking if i go to a shell that's about 10k's away i will get locally made (newer) fuel and also be able to use the coles dockets that mumsy gives me.

i've got an old nissan wagon so i'd have to chuck it on a trailer i'm thinking. how hard is the drum to handle when you get it home full?

[Scalem]

"Peace of mind"? So it's only a feel good thing then without knowing one way or the other?

Why do people spend thousands of $$$$'s on an outboard then risk it all based on nothing more than "Peace of mind" ?? without the facts!

"Risk it all" in this context is overreacting isn't it?. If you want the facts, I know my outboard is designed to run unleaded. "The facts" I was referring to is how much of a difference higher Octane fuel is likely to make on my OB in a trolling trip. I should have been a little more specific, but Geez Kerry, I hardly would "risk it all" by using one or the other. According to any mechanic I have ever spoken to on this subject there is no risk of damage! That's good enough for me! I will certainly enjoy boating without worrying about this detail. ;)

Scalem

[newchum]

hey rodney, how do you transport the drum around? i've been thinking about doing the same thing as you with the 44.
i've got an old nissan wagon so i'd have to chuck it on a trailer i'm thinking. how hard is the drum to handle when you get it home full?

paddles i have ute , i only buy 200lts at a time and the drum is easely slid off the side of the tray. the main thing is tieing the drum in (it's a big misile if let loose)securely

[PADDLES]

thanx rod, it sounds like it'd be just as easy to slide off the back of a trailer.

[Roughasguts]

Drums don't slide off the trailer that easy.

Just need to fill your trailer with empty drums to hold the full one in.

I carted drums on trailers for years, the fuller the trailer with them, the better.

Or you could get an old Leyland P76, there marketing said you can get a whole 44gallon drum in the boot.

What they didn't tell you is how to get a full one out.

[4x4frog]

majed,
For a 1977 Evinrude I'd have a fairly safe bet and say the engine was originally designed for standard fuel which would have had an Octane rating similar to the ULP of today. I know we always were told to run our lawn-mowers on ULP vene after the new PULP came into servos'. I am not sure as to why exactly but the older 2-stroke engines alwasy ran better on std fuel.


I could be totally wrong with my claims though, take it as ypou please::)

[whiteman]

Kerry - they are not listening. Nice try though.

[Kerry]

Kerry - they are not listening. Nice try though.

Doesn't surprise me either! Some don't want to listen either but then eventually the penny has to drop?

[435_Mark]

Spoke to Keith at Sundown when I first bought my 50HP Yamaha 4 stroke about this very topic as I've always been keen on the premium. Kept the records for every drop through every car I've had and the increase in fuel economy has offset the dearer price. With that in mind I was keen to run the premium through the Yamy. Figured a longer burn would be better for the motor. Turned out to be dead wrong! On a trip to Borrolloola I had problems with the motor from day one. (Note: this is using premium fuel I had bought 2 days earlier in Bris.) Motor ran fine down the river until I turned it off to do some casting at a drain. Went to turn the motor on again and the oil alarm started sounding - heart stopping stuff for the owner of a motor that had only done 10 hours!

To cut a long story short the motor was running hotter on the premium with the result that oil pressure could not be maintained. Sitting and waiting for the oil to cool down meant that she could be started and run with no damage. A simple swap back to straight unleaded and she has never missed a beat since.

The OMC factory released a bulletin in 1983 saying unleaded regular or premium with a minimum octane rating of 86 was recommended for 50 - 115HP engines from 1977 to current models (remember this was in 1983 though). If you are in any doubt ring Allan Downes at Downes marine. (no I'm not affiliated etc. etc.) Basically it looks as though you can use either. I'd probably use the unleaded myself, as it seems to let the motor run that little bit cooler.
Cheers,
Mark