lead substitue

[Crazcnuk]

That was 91 'in the old days'.

The formula has been revamped. What we call 87 now is what used to be 91 back then.

[subike]

Have used unleaded 91 fuel in my bike since the day I first got her, runs sweet as. The 2 times I have used the higher octane fuel I found that she ran hotter and did not "feel" right at a constant throttle setting.
NZ has had unleaded fuel for its fleet for arounf 15 years with very few adverse effects to many vehicles. Only the pre 80's british cars , mainly Triumphs, ( not the bikes) had major problems with the additives melting the diaphams in the carbs and the fuel lines.
So unleaded is as good as anything in an XS in my opinion

[yamahansolo]

i found i got 32 mpg with 87 and 38 mpg with 93 octane. it ran ok with the 87 but the miles sucked!

[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.