I bought a new scooter and picked it up today. It’s a Yamaha GTR 125cc. I’m just wondering about the fuel.
It says in the manual to use 92. I has printing above the gas cap to use 92. But the scooter shop guy says put 95 in. He also put half a tank of 95 in.
What am I supposed to do? Use 95? Use 92?
Empty out the 95? Is it OK to mix 95 and 92?
:help:
On the one hand you’ve got two, written, official, documented, independant, verifiable manufacturers instructions that say use 92.
On the other hand you’ve got “the scooter shop guy” saying use 95. Doesn’t seem a tough call to me, especially as its unlikely to matter much either way, at least in the short term.
Sophisticated (eg modern car) engines with knock sensors etc adjust to the octane rating of the fuel and may get extra benefit if you put a higher octane in. I don’t THINK scooters, even EFI ones, are likely to have that capability yet, so a higher octane justs wastes money and in the long term MAY be a bit more likely to foul your plugs.
But don’t sweat about whats already in there. It doesn’t matter.
I didn’t get the EFI model. It’s carburated.
Thanks for the advice. I wasn’t entirely sure about mixing the two types of fuels. 
Jyo Er.
for most scooters 92 gives more torque than 95 i suppose. I don’t know any scientific explanation for this but i’ve made my own test for 1 month period.
and hey, did i mention that 92 has better MPG than 95 too?
[quote=“noripsni”]for most scooters 92 gives more torque than 95 i suppose. I don’t know any scientific explanation for this but I’ve made my own test for 1 month period.
and hey, did i mention that 92 has better MPG than 95 too?[/quote]
Edited from incorrect (backwards 
) information.
As below it was pointed out that my information was inaccurate so here’s a rewrite:
95 or 98 may be used in higher performance engines because of the greater resistance to pre-ignition caused by higher compression. This is simply because of the chemicals added to the fuel to resist fast burn.
Yes, 92 Octane may cause pinking in a higher performance or poorly tuned engine, but is not likely most of the time. 92 is cheaper than 95,or 98 generally and so will often work out more economically. To use a 95 octane your engine would have to have its timing advanced (to pre-ignite) the fuel mixture in order to receive power at the appropriate point of the piston stroke.
Recent tests by the British Automobiles Association have suggested that using 91 octane in 95 octane engines decreases economy by up to 1 litre/100KM (in a car). On the other hand using 95 octane in a 91 octane setup made no recordable difference. Of course the difference will be in the price though, making it more expensive still.
Again. Simply put, don’t put anything in your tank that your handbook doesn’t suggest.
[quote=“sulavaca”][quote=“noripsni”]for most scooters 92 gives more torque than 95 i suppose. I don’t know any scientific explanation for this but I’ve made my own test for 1 month period.
and hey, did i mention that 92 has better MPG than 95 too?[/quote]
Basically 92 burns a little slower than 95
A 92 octane slower burn results in power over a longer piston stroke, providing more torque, but the downfall is at very high speed the fuel cannot burn fast enough to provide enough power for the engine to run faster, thus limiting engine speed or revolution pickup rate. This fuel would then be more suitable for lower performance vehicles which require more torque over power i.e. small engine VS load. Diesel power would be the very extreme in this requirement.
A 95 Octane would basically provide a faster burn/engine speed, but a lower power/torque burn. The other advantage to 95 is that it may burn slightly cleaner than 92. 98 octane therefore is used on the Toyota Prius and other Hybrids, even though it reduces the potential power output due to the design of the vehicle which uses a lower revving engine.
It is often because fast cars use a higher octane that people often assume that the higher the octane the higher the power, but this is not the case. Diesel engines providing a larger torque potential can be geared to go fast too, but acceleration may be inhibited without the use or performance enhancing devices such as turbos.
If your bike is timed and setup to run on 92 then run it on 92. You may only suffer performance using 95, and may use more fuel. You may also cause pinking, or early detonation using 95 which may damage the engine over long periods and cause accelerated engine wear.
There is no benefit to using alternative octane fuels when the vehicle is setup to run on one specific octane. If one wishes to adjust the octane level, then you must consult the owner’s manual, or have the vehicle calibrated or adjusted to do so.[/quote]
I think we’ve answered the OP’s original question, so we’re now getting into petrol-head pedantry.
Sadly, I seem unable to resist that, but I’ll keep it short since we had a (rather acrimonious IIRC) discussion on this quite recently.
Some of what you write above may be true BUT:
(a) The octane number of a fuel is a measure of its resistance to pinking/pinging/knocking/detonation, so using a higher octane fuel (95 instead of 92) will NOT cause pinking/pinging/knocking/detonation, but the reverse.
(b) The phrase “early detonation” sounds worryingly like “pre-detonation”, a widely misused, incorrect term which confuses the two separate phenomena “pre-ignition” and “detonation”. There is nothing “early” about the detonation. In conventional spark ignition engines detonation is always bad and it should not happen at any point in the 4-stroke cycle.
Thanks for pointing that out Ducked. I confuse myself at times. 
Above post edited.
[quote=“noripsni”]for most scooters 92 gives more torque than 95 i suppose. I don’t know any scientific explanation for this but I’ve made my own test for 1 month period.
and hey, did i mention that 92 has better MPG than 95 too?[/quote]
It was wierd but when i switched from 95 to 92 for my Telstar 1.8GL (it doesnt say use 92 or 95 in the manual). I actually got better fuel economy. And same performance. So i basically wasted years of using 95.