Octane - (Australia)

[andrewkafp]

I have an early 80's 50 Merc 4 (Inline) and I run it on Shell lead free fuel (50:1) <br />A Merc repairer advsed me to use Shell Optimax premuim unleaded. The only difference (as far as I know) is that Lead free is 91 Octane and Optimax is 96. The manual specifies above 86 <br />Any comments ????<br /> http://www.shellau.com/oneshell/au/optimax/pdfs/optimax_pds.pdf

 

[roscoe]

Re: Octane - (Australia)

Please ship 20 gallons of the 98 octane, weekly, to the address below. <br /><br />My house<br />The tan one<br />Here in the USA<br /><br />We can't get any gas over 93 octane here.<br /><br />h

 

[andrewkafp]

Re: Octane - (Australia)

<br /><br />Huh??

 

[pwilson]

Re: Octane - (Australia)

Your little 50 horse 4 cyl. Is not a racing outboard.There is no reason to use high octane fuel.In fact try a 1/4 tank of good ole 87 octane regular unleaded. My bet is it will run better than ever.Your mechanic must own a gas station.

 

[andrewkafp]

Re: Octane - (Australia)

Guys<br /><br />The only fuel available here is the 2 above mentioned. We apparently don't get much choice on octane.<br />But .. point taken, if there are no significant differences, I will use the 96..<br />ps The mechanic was referring more to "Less carbon build up " as oppossed to more performance.

 

[tnankerv]

Re: Octane - (Australia)

Andy <br />My suggestion is that you talk to your local outboard repair shop. I was listening to this (great) i-boat forum on octane and decided that standard unleaded was going to be OK. I told my repair guy that I was using it and he was very unimpressed. He reckons that we should still use the Super substitute and when the time comes for them to phase this out we should use the high octane unleaded. He says the standard unleaded will ping bits off the cylinder head. It frightened me enough to empty my boattank into my lawnmower fuel reserve tank. BTW we need to be very wary that we are not using ethanol-laced fuel. I'm told that there were some boats in Brisbane that had nasty things happen to their motors when they added fuel which the garages provided without announcing that it contained ethanol.

 

[Spidybot]

Re: Octane - (Australia)

Howdy folks!<br /><br />Octane value is referred to in more ways. The US rating does not match the European (Aus?) rating (RON). So US 87 equals 90 RON.<br /><br />Apart from that, your Merc is recommended to use at least 87 (90 RON) and there is no reason for going higher. Lead is of no benefit to it, so the advice is to go on as before.<br /><br />High octane fuel has extra additives that prevents detonation ('knocking') in high performance engines (esp. high compression). It contains no more power. <br /><br />These days more petrol companies market their own 'special' fuel. Shell claims that their V-power makes your car faster, cleaner etc. etc. ('feel the difference'). It is a matter of belief - if it was true that a certain fuel would make your car go faster, this would be the only fuel on the market!! Those who say it works in their car can't prove it - they just think they can feel the difference. Ofcourse those fuels costs more..

 

[andrewkafp]

Re: Octane - (Australia)

Thanx Guys<br /><br />Good to see that the post has raised some views.<br />I think for the extra 10c per litre (Aussie for liter LOL) I think that the Shell Optimax with NO ETHANOL sounds good for a mere 25l tank. <br /><br />Oh and Tony.. If it helps, this motor has been running on Shell unleaded for many years, the prev owner tells me with no real problems YET !!!

 

[sony2001]

Re: Octane - (Australia)

Your getting enough delayed burn with both fuels, 96 or 98. Its well above the 87 minimum.

 

[duck-n-pond]

Re: Octane - (Australia)

Interesting about the different rating systems. Here in eastern Canada, rating 87 is the lowest regular unleaded rating you can get. We also have a mid octane of 89, and superior of 91. A note to Andy, I have seen other posts here that recommended against superior as it has more detergents that are apparently not so good for the carb??? As a result, I use mid grade 89. Ironically, when I first got my boat, my second tank of fuel was superior - it was full of water!

 

[Bob Kimber]

Re: Octane - (Australia)

Andy,<br /><br />All outboard mechanics that I know in this part of the world recommend Premium unleaded. this is also backed up by all the dealers of the different brands, they claim the tech bulletins they receive advise this, as premium ULP does not have any ethanol or other alcohol additives but does have superior cleaning additives for carbs or injectors.<br />Bob

 

[Spidybot]

Re: Octane - (Australia)

Just FYI:<br /><br />In Scandinavia it's 92/95/98 unleaded and 95/98 with lead substitute. All RON rated.<br /><br />We used to have 96 and leaded too but those have been removed over time.<br /><br />I can even remember 100 octane from the 1970's. Aero fuel is/was available up to some 105 or 110 if my memory serves me.<br /><br />My first Volkswagen Beetle (1956 model) manual stated at least 87 RON (which is Sovjet level quality)