Age old question - 87 or premium

[iyernat]

As a habit - I have always filled my bikes with premium gasoline. Is it even worth it ? does it help or harm ? Should I just fill with 87 ?

[gn2]

This one has been done so many times before.

There is only one correct answer: Use what the manual says.

[flyingzonker]

I think the manual says use regular, no? The guy at my purchase dealership said that his establishment recommended high octane. I have used both and found no difference in performance. In the beginning of my ownership of this machine I used premium. About halfway through my PCX career I switched to regular--which is probably what you are going to get at the pump anyway whatever you specify and pay for, due to the gallon or so of residual gas in the line from the transaction directly before yours.

[montliz44]

87 sez me. Just one of the joys of my PCX: 100+ mpg on 87 oct gas (Compare and contrast with the 35 mpg of highest-possible-octane gas on my BMW) Yea PCX!

Johnny

[honkerman]

There is no advantage to using higher octane gas in a low compression engine. Use what the manual suggests and save your money.

[you you]

Age old answer - it doesn't matter

[txpcx13]

So Our PCX Manual says : Use unleaded petrol with a research octane number of 91 or higher.... now this translates to > > > As a rule, the recommended octane rating can be determined by subtracting four (4) from the recommended RON number. A vehicle that calls for "91 RON" should use 87 octane gasoline (as measured by the (R + M) / 2 method). Using a higher grade than is required will not usually increase performance.

In USA 87 is fine.

[honkerman]

So Our PCX Manual says : Use unleaded petrol with a research octane number of 91 or higher.... now this translates to > > > As a rule, the recommended octane rating can be determined by subtracting four (4) from the recommended RON number. A vehicle that calls for "91 RON" should use 87 octane gasoline (as measured by the (R + M) / 2 method). Using a higher grade than is required will not usually increase performance.

In USA 87 is fine.

sometimes I wish all countries would use the same octane rating systems. It would make things just a bit easier.

[fantasy2c]

Manual says 87 for my 2015 and I've played with 87,89and 93 and no difference what so ever between the 3 besides 93 costs Alot more then the 87. Similar mpg and butt Dyno is identical. Save your money, stock pcx will not utilize the higher octane.

[Eiron]

As far as I've ever heard/read, the only thing octane level addresses is pre-ignition (knock/ping), not performance. Generally speaking, higher compression engines require higher octane levels to avoid pre-ignition (as increased gas compression inside a hot piston chamber that contains carbon asperities is more likely to pre-ignite). Of course, a side-effect of pre-ignition is reduced performance, so you can maintain performance by using the correct/higher octane level, but not increase it over designed-in limits.

If your engine (car or bike) pings/knocks on the manufacturer-recommended octane, then increasing the octane may restore the performance you're losing from the pre-ignition (assuming that solution cures the knock/ping). Fixing the cause of the pre-ignition might be a better solution. The other consideration may be your riding conditions. Around here (the "Front Range" area of the Rocky Mountains) mountain roads & higher altitude combine to overheat/load/stress your engine, which can set up ideal conditions for pre-ignition, which may lead prolonged periods of piston-damaging knock/ping. Bumping up the octane under these conditions can avoid setting yourself up for pre-ignition.

Basically, you can safely use the lowest level of octane that avoids pre-ignition. For example, I had an older vehicle which spec'd 87 octane. That was perfect for Fall/Winter/Spring, but during 100F Summer months it would ping unless I used 91 octane. (And in the middle of Winter's sub-freezing stretches I could safely use 85 octane.)

The final consideration is to use whatever lets you sleep soundly at night. If you're going to constantly worry by using 87, then it's not worth it.

[waspmike]

sometimes I wish all countries would use the same octane rating systems. It would make things just a bit easier.

They do.

Only US , Canada and Brazil use a different system.

Ron x 0.95 = AKI

So 91 x .95 = 86.5 (87)

[thunderkat59]

After 42 years and lots of bikes, the theory behind the octane/premium stuff I don't disagree with, but what you are really getting is a crap-shoot. Ive had bikes run great on cheepo and sputter on 93. You never know what you are really getting. I just don't believe all gas stations are entirely honest in what they fill their tanks with. Paranoid? Maybe, but that's what I believe. Sort of related, Harley motor drag bike guys use lower octane fuel in their race bikes because the flash point is at a lower temperature and spread out more on the top of the piston. Just repeating what I read, but more to think about if you worry about this stuff. For me, whatever is cheapest, whether its an RR900 or a PCX 125

[honkerman]

After 42 years and lots of bikes, the theory behind the octane/premium stuff I don't disagree with, but what you are really getting is a crap-shoot. Ive had bikes run great on cheepo and sputter on 93. You never know what you are really getting. I just don't believe all gas stations are entirely honest in what they fill their tanks with. Paranoid? Maybe, but that's what I believe. Sort of related, Harley motor drag bike guys use lower octane fuel in their race bikes because the flash point is at a lower temperature and spread out more on the top of the piston. Just repeating what I read, but more to think about if you worry about this stuff. For me, whatever is cheapest, whether its an RR900 or a PCX 125

A bigger concern than octane rating is ethanol content. That stuff is bad ju-ju.

[thunderkat59]

A bigger concern than octane rating is ethanol content. That stuff is bad ju-ju.

Agreed.

I like to give myself (false?) comfort by thinking metallurgy has progressed enough to somewhat mitigate the horror of the evil juice

[gn2]

So long as the ethanol is below 10% all is good.

[honkerman]

So long as the ethanol is below 10% all is good.

put a nail in 10% ethanol gas and let it sit there for a few weeks...see what happens. it will disolve. Stuff is bad for metal. It's bad for rubber. Don't believe the government assurance that it's "safe".

[gn2]

Get your tinfoil hat off.
Honda certify that your scooter is designed to run on a 10% ethanol mix.
If ethanol dissolves metal, why has my metal fuel tank stayed leak free these past three years?
There seems to be a lot of hysteria in the US about ethanol.

[JohnL]

So long as the ethanol is below 10% all is good.

put a nail in 10% ethanol gas and let it sit there for a few weeks...see what happens. it will disolve. Stuff is bad for metal. It's bad for rubber. Don't believe the government assurance that it's "safe".

Are you getting confused with Coca Cola???

Urban myths are wonderful things, as long as you don't take them seriously.

[honkerman]

So long as the ethanol is below 10% all is good.

put a nail in 10% ethanol gas and let it sit there for a few weeks...see what happens. it will disolve. Stuff is bad for metal. It's bad for rubber. Don't believe the government assurance that it's "safe".

Are you getting confused with Coca Cola???

Urban myths are wonderful things, as long as you don't take them seriously.

No, I'm talking about corn ethanol. It's not a myth. It's been done.

[honkerman]

Get your tinfoil hat off.
Honda certify that your scooter is designed to run on a 10% ethanol mix.
If ethanol dissolves metal, why has my metal fuel tank stayed leak free these past three years?
There seems to be a lot of hysteria in the US about ethanol.

vehicles made after ~2000ish were fabricated to withstand the effects better than older vehicles, but it can still cause problems over time. I've had issues with the rubber tubing in the fuel system of my jag, the bits that connect to the fuel injectors. The things just collapsed from being eaten by ethanol. additionally Ethanol is hygroscopic and bonds with water. If a vehicle is constantly used, it doesn't have enough time to bond, but left sitting it will. It's not so much the ethanol that eats a fuel tank, it's the water it attracts that causes it to rust.

If you want to know how it works, here's one source. There are plenty of others.

http://chemistry.stackexchange.com/ques ... nks-or-eng