which gas?

[Crazcnuk]

"I have always put the best stuff that i could buy in my bikes.My 99 ZRX- i dread the thought of putting in a low octane gas."

By 'best' I assume you mean the most expensive..

Ain't marketing wonderful!

I run the lowest octane the engine (any engine) will run without ping. If I could run bunker sea oil, I would.

Low octane = more power, better mileage, lower cost (if your engine is tuned properly)

[FJ111200]

95 RON.

[Sandy H]

fuel

I have a 82 xj 1100 and did a total rebuild.
A bike tech. told me to put 91 in it.
I looked in the manual and it says 87 octaine.
I then talked to the original owner and he said he ran regular.(Canada) Now looking back to 82 what were peaple putting in it then?
I have been running with 91 $1.34 a litre I use Shell all the time.
It is suposed to be the cleanest.
Is this a on going debate?

[boyat68]

Note that Yamaha recommends 91 octane leaded. I use 87 10%alcohol with a little added Seafoam.

[hamjam]

In the picture it says "Research Octane 91 " the Fuels in N.A. are "(R+M)/2" which is Research Octane Number "ROM" plus Motor Octane Number "MON" divided by 2 which works out to be ROM - 4 or 89 at the pumps

87 with seafoam is very gooder with or without alcohol

Jim
Note that Yamaha recommends 91 octane leaded.
I use 87 10%alcohol with a little added Seafoam.

[XSrunner]

It's interesting to see the different octane ratings you guys have over there.87 octane seems really low?. here in OZ we have 91,95,98, and if you can afford to run it 100 octane. I run 98 octane in mine as it has injector/carby cleaners added. so the say.don't know if it helps keep carbs clean. but I will have to try a few tanks of the 91 octane you've got me curious now and i could save a few buck a tank full. 98 oct is $1.70 lt compared to $1.58lt.

[NemisusDM]

Measurement methods

The most common type of octane rating worldwide is the Research Octane Number (RON). RON is determined by running the fuel in a test engine with a variable compression ratio under controlled conditions, and comparing these results with those for mixtures of iso-octane and n-heptane.

There is another type of octane rating, called Motor Octane Number (MON) or the aviation lean octane rating, which is a better measure of how the fuel behaves when under load. MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, a higher engine speed, and variable ignition timing to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern gasoline will be about 8 to 10 points lower than the RON. Normally fuel specifications require both a minimum RON and a minimum MON.

In most countries (including all of Europe and Australia) the "headline" octane that would be shown on the pump is the RON, but in the United States, Canada and some other countries the headline number is the average of the RON and the MON, sometimes called the Anti-Knock Index (AKI), Road Octane Number (RdON), Pump Octane Number (PON), or (R+M)/2. Because of the 8 to 10 point difference noted above, this means that the octane in the United States will be about 4 to 5 points lower than the same fuel elsewhere: 87 octane fuel, the "regular" gasoline in the US and Canada, would be 91-92 in Europe. However most European pumps deliver 95 (RON) as "regular", equivalent to 90-91 US (R+M)/2, and even deliver 98 (RON) or 100 (RON).

So our engines were designed for regular European measurement method of 91 octane or good old US 87 octane.

[TopCatGr58]

Many good points and info provided here!!

Changes over the years in formulations as well as additives like Ethanol....which reduces the amount of power from the gas vs. pure petrol can make a difference, as well as the state of your engine, tuning, even elevation, temps.

I rebuilt mine with $$ Wiseco little big bore kit with increased compression, and didn't want to take a chance of burning holes in my new pistons, so I went with the Premium level. I recently did a little research into using an Octane additive with regular gas, but it's more $$ to use the additive per gallon than to just pump the "good stuff".

Also, modern cars have fancy ignition computers with O2 sensors and FI and such, and can adjust the timing and fuel mixes to maintain performance and prevent knocking when using the cheaper lower octane fuels!! But our machines don't have all of that!

SO....as has been stated, IF your machine knocks with the lower octane fuel, then IF you are certain of your tuning, then using a higher octane fuel may be required to obtain the optimal performance. But if it behaves with the cheaper stuff, consider yourself fortunate, and RIDE ON!!!!
T.C.

[Crazcnuk]

You can actually buy the little knock sensors, that all cars have now, and attach it to the side of your heads.

It hooks up to an idiot light and you can tell if your engine is knocking. Even the knock you would never hear with your ears.

[DJinNH]

Just a follow up. Since first reading this thread, I went ahead a switched from the 93 to the 89 octane. The bike is running great and I haven't noticed any decline in power.

Don

[Crazcnuk]

You should get an increase in power. Lower octane = more power.

[dbeardslee]

My understanding is that the octane rating is a measure of the compressibility of the gas. I run the lowest octane I can without pre-iginition. Mine runs great on 87 and I get 2 miles per gallon better mileage than with 89. Plugs will stay cleaner and it won't dent your wallet as bad.

[MrOzz]

I run mine with 91 to 94 depending on what station i go to.

[tarzan]

I was running 91 when I first got it up and running.I also have a knock above 3000rpm.Someone on here pointed out a service bulletin regarding some 80 and newer XS's.It claims that the knock is not a problem.Someone also suggested switching to 87 octane and it might go away.That really doesnt make sense to me ,but I switched anyway.I still have the same knock that drives me nuts.The bike runs good though.So I run 87 and have all summer.I checked the timing as per manual and it is right.I 'll have to get a degree wheel and see if the pointer is right.Anyway I see no reason to go with higher octane.Unless it were less exspensive than regular.

[Crazcnuk]

There was an issue with '80-'81 XS11's 'knocking' at between 3500 and 4000rpm.

They said this type of detonation does not harm the engine.

However, they made a replacement Vacuum advance unit to get rid of it.

3H5-81683-09-00 Is the replacement part number, but I doubt any are available any more.