What Octane does your bike need?

[Bonz]

There's been a thread going that has gotten into the merits of running a higher octane fuel (91) or regular unleaded (87).

Not looking for ethanol vs non-ethanol, per se. Just in the most general terms the lowest octane your bike runs fine on.

In that thread it has been pointed out a decal on the bike suggested 89 octane in 1979.

There are three choices, please provide any input as well.

[motoman]

To the best of my knowledge, octane ratings were also still calculated differently at that time.

[madmax-im]

I have run with 87 octane ethanol gas without any problems..Most of the time im running 89 octane ethanol free....YMMV

[LakeOber]

I have tried running her on 87, 89, and 93 (they don't sell 91 in Central PA). I honestly think it runs better on 89 than 87. I am sure it is probably all in my head, but I am going to continue to use 89. I did not notice any difference at all between running 89 and 93 though.

[donebysunday]

I don't notice any difference in the performance in the bike or the car but I do get better MPG with the higher octane in both.

[hamjam]

Maybe you're looking for an engineering explanation for a psychological phenomenon.

[BA80]

Mine hates high octane, you can feel the difference. It likes the cheap stuff. Kinda like it's rider.

[motoman]

Mine hates high octane, you can feel the difference. It likes the cheap stuff. Kinda like it's rider.

Agree........and visually, you and that particular bike match well together.

[Radioguylogs]

No poll choice for 93

I use 93 octane in my motorcycles, lawn equipment, boats, Camaro and Grand Cherokee.

I use 87 in the motorhome and Town Car.

The Camaro requires high octane.

In general, I have read that I am wasting money buying high octane because the incremental mileage does not justify the higher cost. (Shhhh the company pays for the Jeep gas.)

I read somewhere that the higher grades of gasoline have less or no alcohol in some cases. I don't really know if it is true in my case, but I'd like to think so.

I really don't believe that high octane will burn the exhaust valves. Maybe someone will come forward with the evidence.

So for lawn equipment, boats, and motorcycles, I buy better gas because it doesn't cost much more for those machines.

[motoman]

I use 93 octane in my motorcycles, lawn equipment, boats, Camaro and Grand Cherokee.

I use 87 in the motorhome and Town Car.

The Camaro requires high octane.

In general, I have read that I am wasting money buying high octane because the incremental mileage does not justify the higher cost. (Shhhh the company pays for the Jeep gas.)

I read somewhere that the higher grades of gasoline have less or no alcohol in some cases. I don't really know if it is true in my case, but I'd like to think so.

I really don't believe that high octane will burn the exhaust valves. Maybe someone will come forward with the evidence.

So for lawn equipment, boats, and motorcycles, I buy better gas because it doesn't cost much more for those machines.

Understand your opinion, but least believe this: The higher octane ignites at a slower rate in lower compression ratio engines, and result is the ignition is still minutely taking place when being exhausted, which raises heat dramadically on exhaust valves. Hope that improved your belief.

[motoman]

.....and as one of many examples, the Honda ST1300 is factory required to burn premium. Reason being, that V4 motor has a 13:1 compression ratio!
Based on my experience in the performance engine building and drag racing world, any motor carrying any compression ratio higher than 10.5:1 should be ignited on premium fuel. In some instances, I added aircraft fuel to tank prior to an NHRA sanctioned drag meet. That was while running a built-up 400c.i. Pontiac Ram-Air IV Judge motor in a 64GTO.

[TopCatGr58]

Sorry, more info than just a VOTE.

I voted 89, but for the first 15 years after my little big bore kit I ran 93 because of the alleged 10.2:1 ratio the Wiseco pistons were supposed to provide...of course I later learned that since mine was the 81 engine, I got less of a compression boost vs. the 78-79 engine. So the last couple of years, I've run 89. I was just worried about pinging that I couldn't hear because of my exhaust and helmet and didn't want to burn holes in my new pistons!

I don't know if I'm courageous enough to try 87, plus, I don't ride every day/week/month even during the season, and gas looses an octane point every month it sits, so I might still be getting 87 from my 89 due to my inactivity!

T.C.

[Bonz]

Hey Brant, I had an ST1300 for a while. It's only a 10.8: 1 compression ratio. I was amazed it DID call premium. The ST 1100 is 10: 1.

I ran 87 octane without any ill effects in the ST1300. I did not drop down to 85 octane even at this elevation however.

It was said a number of posts above, about engineering explanation for psychological feeling. That's what I'm trying to show here. The bikes should not need anything more than a good quality regular unleaded gas.

[motoman]

Thanks for the correction. I understand the ST13's premium requirement, as they are still a bit higher compression ratio than 10.5:1.

[Ctopher87]

I run 90 octane ethanol free

I have ran 87 with and without ethanol. Milage is much better without it. That being said I only use 87 when 90 isn't available. The sticker on my left side cover call for 91 0ctane but that is for leaded fuel. I have noticed my bike runs better with 90.