gas octane for Like 200i - a chemical engineer

[Stig / Major Tom]

My 2 cents on fuel octane for vehicles.
I spent some time with a chemical engineer a while back - here is the short version of his remarks re. fuel for our gas powered engines.

The higher the octane rating the longer the gas will resist combusting in the cylinder.

Lower octanes do not resist combusting as well >> Engines using too low a fuel octane can even "detonate" (combust prematurely - sometimes just on contact with hot cylinder areas during a portion of the pressure phase -importantly, this igniting of gas occurs before it is meant to ) , this then is the unhealthy state of an engine starting to melt itself. Have you ever gone to Mexico with your new car and had issues with the gasoline. It ain't because the octane is too high!

To keep it simple for me, he said : {1} If your engine is running too hot (or even detonating) your octane is too low.
                                         {2} Contrary to layman's logic - 93 octane will never cause your engine to run hotter than 87 octane fuel.
                                          {3}  The above is correct because cheap gas wants to explode NOW - it costs more to refine higher octane gasoline which will resist igniting.
                                           {4} 87 is OK if your owner's manual so states, and your engine is in good repair                                           
                                           {5}  93 runs cooler , not hotter, with those added inhibiters.
At 50, 60, 80 ?? MPG riding my scooter - I'm springing for the good stuff. (and following my owner's manual!)   93 for me.           

[big blue]

Me too!

[Vivo]

Your chemical engineer must also talk to a mechanical engineer... He's right, for a specific engine compression ratio... an engine with a low compression ratio can do good with a low octane fuel and will do no better with a high octane fuel...

To complement your layman terminologies... a higher octane fuel burns slower than low octane... it doesnt explode to all directions but burns from point A (spark plug) and pushes the piston downwards... very efficiently...  a good comparison is you black gun powder versus the new smokeless/slow burning gun powder.. black powder explodes while the present gun powders "burn"... from the primer pushing the bullet out the barrel...

Also, 87 (R+M/2) octane in the U.S. is around 92 (RON) octane in other countries... 

[de dee]

   and the high octane gas usually has no methane in it,.

[SonicSix]

Both of my bikes burn super unleaded, a 2012 Kymco Like 200i and a 2012 Can Am Spyder RT-S SE5.  I don't mind filling up the Like as it only takes a gallon at a time and I can go a long way on that gallon.  The Spyder hurts more because it holds 6 gallons and only gets 30 MPG.  Even so, I put in what the owners manual says to put in... 93 octane.

[91cavgt]

   and the high octane gas usually has no methane in it,.

If you meant ethanol, in the U.S.A., ALL gas has ethanol in it unless you can find a gas station that sells real pure gas which is hard to find in some parts of the country. 


Even though my Like is only getting 50 mpg, I still fill it up with 93 octane from Chevron every time.

[TroutBum]

I have only used Premium gas as labeled in the US. My dealer told me the low compression engines of scooters really only warrants regular grade and that using a higher octane gas is wasting money. But for me the $0.20 to $0.35 difference at fill up isn't enough for me to concern myself with. I waste more money at the vending machines at work each day. 

[Vivo]

I have only used Premium gas as labeled in the US. My dealer told me the low compression engines of scooters really only warrants regular grade and that using a higher octane gas is wasting money. But for me the $0.20 to $0.35 difference at fill up isn't enough for me to concern myself with. I waste more money at the vending machines at work each day. 

Good point... wasting money is subjective... I waste money all the time... booze, impulse purchases, a new knife.... what's a few cents more for a premium item?......

[jprestonian]

Good point... wasting money is subjective... I waste money all the time... booze, impulse purchases, a new knife.... what's a few cents more for a premium item?......

Well, it's really only a premium item if you can make better use of it than something less expensive. Which in this instance is really not the case. But sugar pills make some people feel less pain, have more energy, etc., so YMMV (but will not improve). 
.

[Vivo]

I tried our 100 Octane a few times but it did not give any additional power or performance to my scoot...just really a waste of money...  $.35 may not be much in the States, but it can buy a bowl of hot noodles here...

[91cavgt]

I'll probably try running a few tanks of 87 just to see if the gas mileage improves at all.  In all honesty though, I don't think it will improve since most of my riding is in 55 and 60 mph zones. 

[tclhb]

I don't think our Like is low compression. I seem to remember reading it is 9.5:1.

[TroutBum]

I wish manufacturers would do more to inform consumers so we aren't always debating such topics as fuel requirements.

[Vivo]

@tclhb  -  9 to 9.5:1 is quite the average compression ratio of most naturally aspirated petrol vehicles... 11-13:1 are considered high....  and are mostly found in sports/racing vehicles.... for example, a Z06 Corvette has 11:1 or the Ferrari 458 - 12.5:1 ... these require High Octane to prevent engine from knocking or detonation...

@troutbum - manufacturers usually "recommend" the proper fuel requirement but do not insist on these because we can use regular or high octane as a personal preference and not ruin our engines... especially those engines with ECU's that automatically adjust depending on the fuel being used...  It's is us, the consumers, who just make a big deal out of it and debate....

[AVGuy]

I just use 87 in my Grand Vista and don't have any knocking.

What I wonder is how much gas the pump hose contains from the previous customer. Since I only add 1.5 gallons at the most at a fillup, how much of that is whatever octane was pumped before?