Do I trust this forum or the manual?

[Graydog]

Ok, I have read all the post about low octane VS high octane gas. Seems most agree that Reg. 87 octane works fine. BUT...the shop where I bought it filled it with 93 octane when I left. The manual says no less than 91 octane. I ran several tanks of 93 with no problem. The last tank I put 87 in it. (There was about 1/2 gal of 93 left in it.) Now I notice the bike misses sometimes if I am going over 55 to 60. Not bad....but noticeable and not every time.

Any suggestions as to what to look for if it is not the octane? Did fine with 93 in it. Over 200 miles with no miss. Today, after the tank was half empty, I put 93 in it. Took it out to highway and could not get it to miss.

The bike is an 07 with 1400 miles on it.

Thanks for your help.

[Sarris]

My 2005 Owners Manual states 87 octane on page #7. The difference in octane rating will not induce a miss. Octane is an additive that decreases volatility in high compression motors to negate ping (pre-combustion). The higher the number, the lower the volatility. You can spend more on higher octane, but the truth is your GZ is third world transportation that will probably run on lamp oil, hooch, saki, dog shit, etc.

If you are occasionally getting a high speed miss, I'd have the dealer check it out. Be aware that if they can't make it miss, they'll have nothing to fix. You could have short, a bad ignitor, coil, or something as simple as a bad spark plug.

:yes:

[Orpheus]

I usually run the highest octane available, since even with today's gas prices it costs less than $20 to fill it up. It probably doesn't matter, but for 4 gallons of gas, it's only around $0.80 per tank more (at least around here). I don't have any evidence other than anecdotal, but it seems to me that my bike likes the higher octane stuff too.

[Graydog]

Thanks Sarris and Opheus. My 07 manual states no less than 91 octane. The bike was tuned and a "make ready" was performed as I watched at the Honda shop where I bought it. (That means nothing since I am not mechanically inclined and had no idea what they were doing except that they hooked it up to computers??/gauges and made adjustments.) They even took into consideration that the exhaust had been drilled out with a total of 8 (yes 8) extra small holes. I am going to have that corrected as soon as I have the money. Mean while I think I will run one more experiment with 87 octane and if results are the same I will go back to 93. The difference in cost for 3 gal. is so small.

[patrick_777]

Originally Posted by Graydog

They even took into consideration that the exhaust had been drilled out with a total of 8 (yes 8) extra small holes. I am going to have that corrected as soon as I have the money.

I tapped the holes and installed the appropriate bolts with some blue Loctite. Then painted with some high-heat spray paint.

[Easy Rider]

Originally Posted by Graydog

My 07 manual states no less than 91 octane.

+1 on plugging the muffler holes with stainless steel bolts. I didn't even paint mine and I think they look OK.

We are still not to the bottom of this octane thing. You may have gotten the wrong manual for your bike OR the bike might have originated in Canada.

There are two different methods of measuring octane. "Regular" unleaded measured with the US test comes out 87, using the European test (I think also used in Canada) it comes out 91. Rest assured that your bike does NOT require fuel with a US octane rating higher than 87.

A teeny tiny number of bikes designed for "regular" SEEM to benefit from higher octane. Yours might be one but the odds are heavily against it. Your experience with going back to regular may have more to do with the brand/quality of the 87 gas you got than with the actual octane rating.

Sometimes the higher octane fuel gets its octane boost with a higher percentage of ethanol. In that case, you would be trading the higher octane (that you don't need) for slightly lower gas mileage (which you don't want).

Do whatever makes you and the bike feel best.
Except for a few pennies from your pocket, it won't hurt a thing.

[music man]

Wait Easy Rider are you saying that ethanol or ethanol blended gasoline in this case will make you get worse gas mileage. Cause if that is correct that sucks cause probably over half of the gas stations here have high ethanol blend gasoline. By the way not questioning whether your right, just want to know if I understood you right.

[patrick_777]

Yes, that's exactly what he's saying. And he's absolutely correct.

Ethanol has a lower burn point and energy output than gasoline. It doesn't burn as efficiently, and to get the same energy out, you have to use more of it. Therefore, higher ethanol = lower mpg.

[jonathan180iq]

I can show you on my mileage graph where I purchased ethanol blended gaoline, only 10%, and you can see a significant decrease in my mileage. It yielded the lowest mileage that I have ever seen on my Gz; 61 mpg. Over the course of a year and a half I am averaging 67 mpg.

Also, in response to your original question, consider this forum as a supplement for the service manual. The manual being tops. Sometimes we can just explain things a bit easier than the manual and you can come here to get opinions and experience on certain techniques.

Easy pretty much took care of the octane question.

[music man]

Yes, that's exactly what he's saying. And he's absolutely correct.

Ethanol has a lower burn point and energy output than gasoline. It doesn't burn as efficiently, and to get the same energy out, you have to use more of it. Therefore, higher ethanol = lower mpg.

Well That really bites, I thought that I had been seeing a drop in gas mileage but haven't really been running deep enough into the tank lately to really tell. Like I said I don't know about where all you guys live but here in hot springs you can't hardly get gasoline that is not high in ethanol content.