91 vs 95 vs 98
Submitted by Kakkerlak on Sun, 2017-01-15 17:17
I have a yamaha F90 on my boat and was wondering what fuel to use. I was told 98 was much better for the jets but 98 is very expensive so I've been compromising with 95 untill I fillled up the other day and saw the fuel contained 10% ethonol which cant be great for marine motors...I think. Is 91 ok to use or will I run into major issues in the long run. Any advice appreciated.
Marineboy
Posts: 839
Date Joined: 14/03/14
Fuel
yamaha recomend 91 octane for all their reasonably current 4 stroke motors.
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Matts123
Posts: 58
Date Joined: 13/11/16
I was advised to run 91 in
I was advised to run 91 in my Yamaha 100 by my mechanic (04 model 4stroke)
Never skipped a beat.
Foxy
Posts: 13
Date Joined: 14/03/06
Fuel
Used to work at the Refinery.
91 has a higher proportion of butane and cracked spirit [made from heating up thick black stuff left over after the good stuff has been distilled off , to 500 deg and breaking up the hydrogens and carbons using a catalyst to make a new molecules]
A few other things get made made too ..call them impurities.
It's definitely not as "clean" as 95 or 98 ..95 has less butane than 91 .
I'm pretty sure 98 has no cracked spirit in it but regardless is much cleaner.
I have run nothing but 95 or 98 in my 90 Evinrude 2 stoke for 14 years. Excellent ..Always a first time start.
I've had a Yammy 115 4 str for the last 3 years and run nothing but 98 .
Bluedog
Posts: 251
Date Joined: 28/07/11
I was under the impression
I was under the impression that 98 causes outboards to run too hot.
BlueKiaser
Posts: 422
Date Joined: 22/04/15
I'm no expert on fuels, but I
I'm no expert on fuels, but I didn't think that the premium unleaded (Octane 95) or 98 RON (Octane 98) contained Ethanol (at least here in Australia from the major Servos), whereas, if the bowser says E10 then it has the 10% Ethanol.
About a year ago, I had issues with my fuel. The first thing the marine mechanics asked was whether I had used any fuels with Ethanol. They mentioned that the Ethanol is causing a great deal of problems ... a common symptom a gooey like substance. As I understand it, the Ethanol is more of a solvent and when initially used in older boats/fuel tanks/fuel lines, can strip dirt and rust disolving it and thus more likely to cause problems with fuel supply, filters, fuel pumps, etc...
At the end of the day, I don't believe I had used any fuels with Ethanol, mostly Caltex Vortex 98 Octane. I suspect my troubles were more due to my own neglect of letting the boat sit idle for some years about a year before the problem occurred.
Anyways, I'm still a big believer for spending the extra money on the Octane 98 Fuel. The fuel is more likely to be of a better quality and it should keep your fuel system cleaner. Yep it costs more ... about 15% more than standard Unleaded (91 Octane), but when you consider all costs/benefits, especially if you get your motor serviced professionally, the extra fuel costs are offset by less servicing problems/costs and better performance.
JohnF
Posts: 2836
Date Joined: 07/07/10
91 burns faster and will make
91 burns faster and will make more power than 95 or 98 IF the motor has been tuned (spark advance, compression or boost) for 91.
If your motor does not ping on 91, then use it. I have a supercharged Varado 250 and only use 91 (it is tuned for max power with 91 in the factory). 300 Verados run more boost and need 95 or 98 or else they will self retard and loose power (and possibly run hot).
I have a high boost turbo race car and only use 98 (it was tuned by me to "just" hang together on 98........). It really wants E85 with +105 octane.......
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Kakkerlak
Posts: 114
Date Joined: 26/03/15
Cheers
Cheers for all the advice!!!!