premium/optimax in yammie 50 4 stroke

[Glind]

Has anyone tried premium or optimax in a Yamaha 50 4 stroke. I'm not too sure if this type of high octane fuel is suitable and if it will affect the engine ie valves etc.
If the higer fuel is okay, do you run this fuel all the time or ever few tanks. Cheers Tim

[Jack_Lives_Here]

Tim,
I'm on my 4th tank of Optimax - same motor as yourself. The yammy loves it. I was a sceptic at first but it DOES give me more km's to the tank for sure. Mines just ticked over 192hours, just on 16 months old.

[Big_Kev]

Tim I have been alternating between premium and regular in my 60 yammie 4 stroke(same donk in real terms).
Only put 27hrs on her so far .
Last fill was with regular.I found the engine harder to start (usualy just a flick of the key)and didnt have the same sort of zing so to speak, seemed to chew more as well.
Will be pumping in the premium next to qualify the performance as being noticeably better. And being in Brissy I will only get the Shell or BP the BP is handy on the way to the water so it usually gets to go.
I would like some feedback as to weather an upper cylinder lubricant would be beneficial when running the premium fuel.

Cheers Kev

[Kerry]

What's the fuel octane rating in the manual?

Cheers, Kerry.

[Big_Kev]

Kerry
The Yamaha owners manual of which was supplied with the motor states that the "recomended gasoline ; Regular unleaded gasoline."
Also,
"If knocking or pinging occurs, use a different brand of gasoline or premium unleaded fuel. If unleaded gasoline is not available, then premium gasoline can be used .
If leaded gasoline is regularly used, engine valves and related parts should be inspected after every 300hrs of operation."
No recomendation is made toward the octane rating of the fuel.
I think that this comment is open ended (How long is a piece of string so to speak).
I do know that Leaded Fuel is no longer available in Australia, but I still use premium fuel thinking that this fuel may come with more of a gaurantee as to its chemical make up.
And the experience I have had (not only with my boat) providing a seemingly better performance from the engine.
Therefore would we be better to run an aditive to the fuel to extend the life of the engine or would we be wasting our time and money?

Thanks Kev

[Kerry]

I suppose the quality (or non quality) of our fuels makes it a bit hard these days for makers to be specific. Certainly becoming less of a choice and probably I would tend to think 2S's and 4S's could vary a little in what might be the best.

Fuel additives ??? I don't really know about some of them. I'm a bit wary of fuel additives especially some of the claims made about things.

With some of the additives one might as well run premium and be done with it as that's about all some of them do.

Cheers, Kerry.

[dazza]

Hi Guy's
Just had a look in the owners manual for my Honda 40hp.
It says "Use automotive unleaded gasoline with a Research Octane Number of 91 or higher (a Pump Octane Number of 86 or higher). Use of leaded gasoline may cause damage to the engine."
There is also a bit about "gasohol" (ethonol and methanol fuel blends). Basically it says don't use fuel with more than 10% ethanol. It also goes on about methanol blends.
I apologise for my ignorance but, what is the octane raiting of unleaded and premium?
Is the performace advantages worth the extra cost?
I guess when you use 3 fiths of bugger all it dosent really matter
Cheers
dazza

[Kerry]

Dazza, RON for Unleaded is 91, Premium 95 and LRP 96. I believe stuff like Optimax is higher again at around 98 RON. RON is higher than Pump Octane Number

Fuel octane levels fluctuate anyway so there's no real consistency (close enough but) between batches.

Apart from what high octane fuels might "appear" to do putting high octane fuel in a low-octane engine is nothing but a waste of money, which means engines designed to run on low-octane fuel gain no benefit from higher octane fuel.

Best performance comes from knowing exactly what octane level fuel the engine requires.

Cheers, Kerry.

[Lucky_Phill]

Having said all that guys, and going off on a tangent ( as usual ).

With the price of fuel at 71 cpl near Easter, I filled the Jackeroo ( 3.2 V6 petrol ) with Optimax( 79cpl ). Not expecting much from the exercise.......surprize surprize, ( as Gomer would say ), not only did the car perform better, while towing in particular, the economy actually improved. We're not talking hundreds of k's better, but noticable.

So I've filled the work ute ( 98 4ltr Ford ) with the Optimax as well. Haven't noted the economy but, performance has increased, ( just ask the little Nissan 300ZX that tried to do a number on my from the inside lane at the lights ;), OH ! did I say That ? ).

Obiviously, these fuels work for some cars / motors and not for others ( Kerry ), just find your place.

Phill ;D 8)

[dazza]

Thanks Kerry,
Can I assume that if the manual says RON 91 or higher it will run better on premium/optimax?
I guess it might be a matter of running a bit through and comparing the difference
cheers
dazza

[davo]

I had a V6 Mazda 626 and on a dollar per Km basis it was far more economical to run on premium. Some motors it makes a difference other none. My Holden Rodeo it made no difference. The Mazda got nearly 100Km extra out of a tank.

[Kerry]

Dazza, probably no harm in trying it but I really wouldn't go straight to the highest octane stuff like optimax. If it's tuned/timed for 91 then 96/98 RON might requrie different timing?

High octane fuels burn slower, are harder to ignite and technically the higher octane, slower burn rate can actually reduce power.

Cheers, Kerry.

[dazza]

Hi Kerry,
thanks for the advice. will try a few tanks of different petrols and let you know how i get on.
cheers
dazza