Q about octane/no ethanol

[Bergman16]

I was very happy to learn through a post here (that led me to pure-gas.org) that a widespread convenience store chain in NYS--Stewarts--sells non-ethanol gas at every station. But, it's only at the 91 octane level. I generally run 87 on the bike, and she runs fine.

Besides the expense, is there a downside to 91 octane on these old bikes? I couldn't tell any difference on one tank in terms of performance.

[speedlimit85]

Non ethanol is 90 or 87 octane here. I've been using 90. Next tank I'll try 87 and let you know if there is a difference.

[motoman]

I was very happy to learn through a post here (that led me to pure-gas.org) that a widespread convenience store chain in NYS--Stewarts--sells non-ethanol gas at every station. But, it's only at the 91 octane level. I generally run 87 on the bike, and she runs fine.

Besides the expense, is there a downside to 91 octane on these old bikes? I couldn't tell any difference on one tank in terms of performance.

IMO, run the 87octane. Compression ratio of these motors isn't high enough to justify 91 and higher octane. What it amounts to is, the higher octane fuel ignites a tad later which compensate for high compression ratios, which in itself will cause fuel/air mixtures to ignite a tad sooner.

[Bonz]

IMO, run the 87octane. Compression ratio of these motors isn't high enough to justify 91 and higher octane. What it amounts to is, the higher octane fuel ignites a tad later which compensate for high compression ratios, which in itself will cause fuel/air mixtures to ignite a tad sooner.

In other terms not expressly stated thus far, since higher octane gas ignites later, therefore it will burn later, and in the face of lower compression, will be burning still when the exhaust valve is open and depositing carbon onto the backside of exhaust valves, which can shrink valve clearance and burn an exhaust valve worst-case.

[Bergman16]

In other terms not expressly stated thus far, since higher octane gas ignites later, therefore it will burn later, and in the face of lower compression, will be burning still when the exhaust valve is open and depositing carbon onto the backside of exhaust valves, which can shrink valve clearance and burn an exhaust valve worst-case.

Thanks, I was afraid of something like that. Too bad.

[motoman]

Thanks, I was afraid of something like that. Too bad.

'Too bad'.........naw, tis a good thing. Think of the money not wasted at the pump, or an overheated exhaust valve or two or four.

[Bergman16]

'Too bad'.........naw, tis a good thing. Think of the money not wasted at the pump, or an overheated exhaust valve or two or four.

yeah...I feel better already!

[BA80]

My bike HATES high octane. Loves the cheap stuff.

[donebysunday]

I myself would rather use the 91 non-ethanol and run a few oz. of MMO every few tanks than that worse for your engine E10 crap.
This is exactly what I did with my new 79SF until it was not new anymore 6 years later with 55K on the clock.
I sold it to my neighbor, he took it to Mexico once and made the round the great lake trip twice. It ran just fine till he crashed it

I was very happy to learn through a post here (that led me to pure-gas.org) that a widespread convenience store chain in NYS--Stewarts--sells non-ethanol gas at every station. But, it's only at the 91 octane level. I generally run 87 on the bike, and she runs fine.

Besides the expense, is there a downside to 91 octane on these old bikes? I couldn't tell any difference on one tank in terms of performance.

[Bonz]

I think you have said it yourself best, you couldn't tell a difference between them in performance. That seems to be a de-facto answer. . Stick with the lowest octane that doesn't knock or ping. The bike should run the best and make the most power.

[MPittma100]

Decal

Decal on bike says to use 89 octane fuel from 1979.

[bikerphil]

That non-ethanol fuel sure is great for bikes that get infrequent use.

[cajun31]

lucky for

us that we have ready access to 87 non ethanol. I also second what Done said about the MMO in the gas tank. I put a couple capfuls in every tank. I notice the difference when on the road and I don't put the MMO in. Valves get louder.

[speedlimit85]

87 no ethanol performs the same as 90 no ethanol. Oddly, 87 costs more than 90.

[Bonz]

All things equal 87 octane will you get a little performamce versus 90 octane in the XS. 90 octane burns slower and the XS (and all other engines designed for lower octane fuel) doesn't combust 90 octane as fully before the valves start opening on the exhaust stroke. Interesting that 87 non ethanol costs more than 90 non ethanol. That must be a local thing where you are?