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For the past 3 weeks since I've had my bike, I've been unknowingly using the wrong octane fuel (87) instead of the 91 recommended by the manual. Is this hurting the bike in any way?

Sorry if this seems like a stupid question
 

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regular gas, 87, is recommended. that 91 figure you see is based on a different calculation.
 

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SV manual recommends 91? i thought it was 87....

anyway, higher octane means more resistance to detonation (and sometimes more detergents added to gas). using higher doesnt add anything to engines that are not smart enough to advance timing, although may be a tad better for the detergents. 87 is fine if you dont have any knock (which you shouldnt have with an SV on 87 because its not an advanced/turbo/finetuned engine). i remember SV requiring basic gas though (ie 87 or 89 or whatever the lowest is). youre in the US right? (octane numbers vary by country because of different measuring methods)
 

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Ethanol will worsen gas mileage and it also can cause corrosion in the fuel system. How much is arguable, though.

One thing about ethanol, though, is it's octane rating is through the roof. I'm actually thinking about eventually converting my Mustang to E85 just for the free horsepower (with appropriate adjustments in spark timing, of course). Only problem is I'd be filling it up every time I took it out, and there is currently only one E85 dealer in Mesa.

Flexfuel vehicles automatically adjust the ignition timing and a/f ratio according to whatever you fill it up with. Pretty cool tech if you ask me, but I doubt many owners even use it. E85 may be cheap, but like I said, gas mileage is horrible.
 

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Ethanol also decreases your mileage:

Compared to gasoline and diesel, the gas mileage in ethanol is the least. Ethanol only has 30.40 energy content, which yields about 34% less gas mileage than gasoline. Because E85 fuel only has around 80% of the energy of gasoline, full usage of the said fuel alternative remains to be in question. Certainly, the lack of energy content in E85, which accounts for the two percent to 30 percent loss in gas mileage, is not to be discounted especially by the public. Also, it has been observed with fuel combination, gas mileage drops as there is less gasoline present in the fuel mixture. Taking a look at gasohol, which is a mixture of 10% ethanol and 90% gasoline, energy content is at 28.06 MJ/L. If you will compare this E85, which is a mixture of 85% ethanol and 15% gasoline, energy content is lesser as the ethanol content is much higher than the gasoline. Now, you can only imagine how less the energy content is in pure ethanol. E100, which is the pure ethanol fuel, only has 19.59 MJ/L energy content. This is way far behind the 29 MJ/L energy content that pure gasoline gives, hence using pure gasoline yields more gas mileage.
(http://www.cleanairtrust.org/E85-Gas-Mileage-Consumption.html)
 

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Ethanol will worsen gas mileage and it also can cause corrosion in the fuel system. How much is arguable, though.

E85 may be cheap, but like I said, gas mileage is horrible.

+1. Older vehicles hoses and carb gaskets are more susceptable to swelling when ethanol gets in the 10% ranges. My YZF's manual explicitly says no more than 5%. Then again it does require 92oct min anyways and only the Kwik Trips here have 100% gas on premiums. Its easy to tell how much less power it has when I have to use 10%. Doesnt have the "kick" it normally has. Already replaced the fuel pump gasket twice due to high ethanol fuels. Also drops from 38mpg ave to 30mpg when I have to use that garbage.
 

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first time, ok, 2nd time? wtf? wasn't the new gasket "new"?

Uh yeah, direct from Yamaha. Considering I've had this bike since 97, first one leaked around 40K (rubber was all gooey too), 2nd one around 75K. Unfortunately Yamaha doesnt make a gasket for this bike that can handle ethanol (they quit making it in 98). Its not hard to replace and not that $$ either.
 

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Also drops from 38mpg ave to 30mpg when I have to use that garbage.
Not to be a dick, but I call BS - 22% loss in fuel efficiency with E10? I'm anti-ethanol (depending on the source anyway) but this seems ridiculous.

Unfortunately Yamaha doesnt make a gasket for this bike that can handle ethanol (they quit making it in 98). .
Like the poster before you so eloquently put it - WTF? Make a gasket out of something else then that will handle the ethanol.
 

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I've seen a 5% increase in mileage when going to Ethanol-free 87 over 87 E10 in the SV, but each engine responds differently.

In addition to promoting corrosion in the fuel system, Ethanol also increases the chances of rust forming in the tank. Generally, it's always a good idea to keep the tank as full as possible anyway.

The intermittent fuel line leaking (TB connection line) on the 2nd gen SV may be related to Ethanol in the gas.
 

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How about asking what oil to use?



:facepalm:
 

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all newer bikes & cars are designed to run with up to 10% ethanol

the biggest problem with ethanol gas is with carbs and not FI when you don't ride regularly, the ethanol will evap and leave residues that clog carbs, not a problem if you dont let your bike sit for weeks at a time

the engines ethanol affects the worse is small engines, lawnmowers, snowblowers, rototillers, etc. when storing for more than a few days, turn the fuel off ( install a valve if there isn't one) let the engine die by running out of fuel rather than just turning it off, then drain the float bowl. don't leave fuel in the carbs to evap and you shouldn't have a problem
 

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the engines ethanol affects the worse is small engines, lawnmowers, snowblowers, rototillers, etc. when storing for more than a few days, turn the fuel off ( install a valve if there isn't one) let the engine die by running out of fuel rather than just turning it off, then drain the float bowl. don't leave fuel in the carbs to evap and you shouldn't have a problem
It also makes them run lean. When Ethanol first started being blended into gas there were numerous problems with small 2-strokes sticking because of the leaner mixture. Manufacturers have since adjusted the mixture to compensate for Ethanol blend, and now you run slightly rich (on newer "adjusted" engines) if you run Ethanol-free.

Generally, it's just a good idea to stay away from Ethanol in anything except a newer model auto IMO.
 

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It also makes them run lean. When Ethanol first started being blended into gas there were numerous problems with small 2-strokes sticking because of the leaner mixture. Manufacturers have since adjusted the mixture to compensate for Ethanol blend, and now you run slightly rich (on newer "adjusted" engines) if you run Ethanol-free.

Generally, it's just a good idea to stay away from Ethanol in anything except a newer model auto IMO.
fwiw, you can buy premixed 2stroke ethanol free in 40:1 or 50:1 from Bailey's Logging Supply, it's called SEF (Small Engine Fuel) and made by VP Fuels with 93 octane, eeekspensive though, $35 for 6 quarts
 
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