another e10 question

mommicked

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Dec 15, 2009
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My boat mechanic said to run 89 octane in my 03 F90 yamaha.he says e10 loses 3 or 4 octane points in two or more weeks of storage.yamaha recomends 87 oct.any comments on this issue?
 

JB

Honorary Moderator Emeritus
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Mar 25, 2001
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45,907
Re: another e10 question

The losing octane stuff is a myth, and even if it was true your engine would run just fine on 80 octane.

Yamaha knows a lot more about that stuff than your wrench.

Use 87 octane. 89 probably wouldn't hurt anything except your pocketbook.
 

mommicked

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Re: another e10 question

Thanks for the reply,by the way I have used it last gas up,and the motor seems to run stronger.?
 

99yam40

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Sep 7, 2008
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9,195
Re: another e10 question

The mind does great/strange things, or maybe you have some proof that it runs stronger.
like he said they are designed to run on 87. The higher the octane the slower the fuel burns, too low and it will cause problems with piston slap or knock by burning fast enough to push down on piston before TDC.
If gas sits too long without stabilizers the it needs to be dumped/ used some where else
 

rodbolt

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Sep 1, 2003
Messages
20,066
Re: another e10 question

use the blue startron,or its equivalent at every fillup.
by the time octane loss is evident its called phase seperation.
phase seperation,even with a stabilizer can happen in as little as 2 weeks depending on physical conditions.
mostly humidity and tank vent types.
remember ethanol is hygroscopic.
hygroscopic means the ability to absorb moisture from the air.
once the ethanol is saturated it seperates from the gasoline base and settles to the bottom as a watery goo.
carbed motors get lucky as the motor simply wont run,the EFI guys ususlly break a motor cause they keep trying to run it even though its running poorly.
the base stock of E fuels are typically 8 points or so lower before blending with Ethanol due to the fact the ethanol is an octane booster until it seperates.
make sure whatever stabilizer you use contains a biocide.
bacteria can live in the water absorbed by the ethanol and feeds on the surgars in the ethanol then the dead bacteria clog filters.
kinda like the algea and bacteria found in disiel fuels.
as far as octane, the higher the octane the slower it burns for a given compression ratio.
if the engine is desined to run on 87 octane at high speeds high octane fuel can actually make less power and more carbon buildup.
we can control how much air goes into a cyl,how much fuel and when the fuel ignites.
the ONLY thing we cannot control is when the fire goes out.
at 6000 RPM we have to get the air fuel mix into the cyl,compress it,light it and the fire is mostly going out before the next intake cycle.
slow burning fuel may or may not be able to do that.
I dont like to see any E fuel used after stored 3 months or longer even if it was stabilized.
Efuels are the most expensive hoax ever shoved down the throats of americans by our govt.
 

ENSIGN

Lieutenant Junior Grade
Joined
Jun 21, 2009
Messages
1,179
Re: another e10 question

Buy only as much as you're going to use,Drain the carbs when you're done and invest in a fuel water seperating fuel filter.
 
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