# High Octane



## Spectrum (Jan 6, 2013)

I'm no fan of E10 and had always been told to stay with regular grade gasoline.

5 miles down the road is an airport (Sanford Maine) that offers Mogas (91-oct. ethanol free) gasoline.

So in the interest of getting it right a quick search brings me to this B&S page:

*What should be the octane rating of my fuel?*

It is recommended that fuel with a minimum of 87 octane / 87 AKI (91 RON) is used in our engines. For altitudes above 5,000 feet (1524 meters), a minimum 85 octane / 85 AKI (89 RON) gasoline is acceptable.
Since small engines operate at relatively low compression ratios, knocking is seldom a problem, and using gasoline with a higher octane rating is unlikely to offer any benefit.
For related information regarding fuel, please visit our Fuel Recommendations FAQ.
*NOTE:* We DO NOT recommend the use of gasoline which contains alcohol, such as gasohol or E85. Gasoline used MUST NOT contain more than 10 percent Ethanol and MUST be removed from the engine during storage if it is not already treated with our Advanced Formula Fuel Treatment & Stabilizer. DO NOT use gasoline containing Methanol. DO NOT use E85 fuel.


<SNIP>


So my read is that going above 87 at a normal altitude will only nick my wallet and if it's the escape route from E10 it's the best thing since sliced bread. Am I missing anything?


Pete


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## db9938 (Nov 17, 2013)

I would say that your appraisal is accurate. But, I would add that the lack of ethanol would be insurance against other ethanol related repairs. However, if you run it dry, no ethanol is left to do any damage. 

But this is just my opinion.


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## caddydaddy (Dec 10, 2014)

Yes, it's just going to cost more. I wouldn't go too high with the octane, you'll start to lose power. Unless you increase the compression ratio! 
Hmmm....now you have me thinking of another snowblower mod! haha


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## Sblg43 (Jan 18, 2014)

I use only non-ethanol gasoline in all my small engines (including my motorcycles). Around here, that usually means the highest grade at the pump. The extra money is not a significant amount since my gas cans are only 2.5 gallons.

I do small engine repair on the side and I must say that I have had to clean or replace many a carb that had residue from the ethanol clogging things up. These were from people who don't properly store their equipment. 

That ethanol has generated a lot of money for me with the two stroke engines. The thin fuel lines on the trimmers, chainsaws, blowers, etc... get messed up pretty good with ethanol.

I once read it this way (and I may be wrong) - "Ethanol comes from corn. Corn is a form of sugar. Would you put sugar in your gas tank?"

My two cents.


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## caddydaddy (Dec 10, 2014)

Sblg43 said:


> I use only non-ethanol gasoline in all my small engines (including my motorcycles). Around here, that usually means the highest grade at the pump.


Not sure where you are, but most pumps that I've seen across the country have 10% ethanol in all octane grades, unless they specifically say that they are ethanol-free!


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## AriensSnowman (Dec 9, 2014)

Same thing in MA, all grades of gas have 10% ethanol. 93-94 octane has the same ethanol as 87. If you have an option to buy gas with reduced ethanol consider yourself blessed.


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## HCBPH (Mar 8, 2011)

*Fuel*



caddydaddy said:


> Not sure where you are, but most pumps that I've seen across the country have 10% ethanol in all octane grades, unless they specifically say that they are ethanol-free!


Either ethanol-free or nonoxygenated in my area.
Around here at least 1 station has a pump listed for classic/collector vehicles and small engines. No alcohol in that gas. You pay a premium for it but it's all I use in my small engines along with topping off the tanks in my Vette and TBird before winter hibernation.


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## TOTHEMAX (Dec 7, 2014)

I use non ethanol 91. 91 is as high as I can get in MT


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## Kenny kustom (Nov 25, 2014)

What about using 100LL avgas?


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## ToroGuy (Jan 12, 2014)

caddydaddy said:


> Yes, it's just going to cost more. I wouldn't go too high with the octane, you'll start to lose power. Unless you increase the compression ratio!
> Hmmm....now you have me thinking of another snowblower mod! haha


You couldn't be more wrong. You do not lose power with more octane, thats totally incorrect. Realistically these engines run low compression at low RPMs meaning 87 octane is more than enough. If you can find gas without enthanol at any octane above 87 run that and only that. We are lucky here in Ontario to have Shell 91 and CT 91 which are enthanol free.


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## 1894 (Dec 16, 2014)

Fastrac kinda near me has 91 octane premium that is ethanol free . 3.02 $/ gal todays price it's the only non-ethanol grade they have. 
Price comparison , reg is 2.55 $ / gallon there.
I only use the eth free in my mower , chainsaws , and now my snowblower.


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## TooTall9957 (Dec 14, 2013)

I'm extremely lucky to have a station nearby that offers two octane levels(89 and 91) of ethanol free gas. I run ethanol free in everything. You actually get better mileage with the ethanol free gas, as the ethanol only has 25% of the energy of gasoline.


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## caddydaddy (Dec 10, 2014)

ToroGuy said:


> You couldn't be more wrong. You do not lose power with more octane, thats totally incorrect.


Please prove me wrong, but I've always heard that higher octane fuel is harder to ignite, and without the increased compression ratio that the fuel was designed to be used under, it will burn slower and the engine will lose power. 
To what extent on such a small engine as a snowblower, and at what octane increase you'll notice a difference, I don't know. 
Either way, I wouldn't run 110 race gas in my blower just because!


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## [email protected] (Nov 21, 2011)

If the engine manufacturer calls for "86 octane," there is no reason to run higher octane fuel. 

The exception to this is if the 86 octane contains ethanol, but the available higher octane is ethanol-free. In such a case, the ethanol-free fuel will have a longer shelf-life, often a nice advantage in equipment that is not used year-round. 

The alternative is just to simply drain the ethanol-type fuel from the tank at the end of the season. Then adding fresh fuel at the beginning of the next season will ensure reliable starting and smooth running.

Decayed / "stale fuel" is the #1 reason for poor running and/or no/hard starting complaints.


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## crazzywolfie (Jun 2, 2014)

i personally run ethanol free 91 octane gas in all my small engines. i usually don't even bother draining the fuel out of any of my carbs. no ethanol no troubles. my engines usually fire up like i was using them yesterday even if they sit for 6 months. if more people understood how bad ethanol is for small engines they would not run it. it is cheaper to spend $12 more a year(assuming you use $100 worth of fuel over the winter) on good gas than it is to pay a mechanic about $50+ per year or every other year to clean your carb.


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## AriensSnowman (Dec 9, 2014)

caddydaddy said:


> Please prove me wrong, but I've always heard that higher octane fuel is harder to ignite, and without the increased compression ratio that the fuel was designed to be used under, it will burn slower and the engine will lose power.
> To what extent on such a small engine as a snowblower, and at what octane increase you'll notice a difference, I don't know.
> Either way, I wouldn't run 110 race gas in my blower just because!


Octane ratings measure a gasoline's ability to resist engine knock, and there is absolutely no benefit to using a higher octane rating than your engine requires nor will you loose power. A higher octane means the gas can be compressed more before it ignites, which is why higher octane is required in high compression engines. 

Mythbusting Octane, The Truth About Gasoline


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## ToroGuy (Jan 12, 2014)

AriensSnowman said:


> Octane ratings measure a gasoline's ability to resist engine knock, and there is absolutely no benefit to using a higher octane rating than your engine requires nor will you loose power. A higher octane means the gas can be compressed more before it ignites, which is why higher octane is required in high compression engines.
> 
> Mythbusting Octane, The Truth About Gasoline


Thanks was just going to post this. Yes higher octane is not required but here where I live you will only find ethanol free gas in 91 octane, so I will always use 91 ethanol free in all my equipment.


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## pfn (Dec 24, 2010)

I recently purchases some avgas from the local airport and the guy selling it said that avgas will not leave any varnish as it evaporates. He said some of the (not to smart imho) pilots leave gas in their aircraft for years with no ill effects. I do not know if this is so but there you go...


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## Ryan (Dec 13, 2013)

Living up at 6000ft running 91 octane in engines not designed for it generally does result in poorer fuel economy and performance. We have 2 stations near me that sell ethanol free 91 octane in the spring and summer months but have to stop selling it in the fall and winter months.


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