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May 20, 2011 | 01:56 PM

#41

NoCoLoco

Road Warrior

Joined: Jul 2009

Posts: 1,979

Likes: 2

From: Northern Colorado

For those of you who feel that 91 octane is not necessary, do you also use a lighter weight oil or put less air in the tires? What else is the manufacture lying about?

May 20, 2011 | 03:08 PM

#42

svt_ct

Intermediate

Joined: Apr 2011

Posts: 31

Likes: 0

From: Connecticut

Higher octane gas has a lower energy content than regular gas but more energy can be extracted from the gas than low octane by using higher compression. The higher octane + high compression engine has higher cylinder temperature and pressure (compression) which allows more efficient combustion (more power + mpg) with less pollution.

Engines designed to run on a certain octane will not perform as well when using lower octane. In cars the engine computer will retard the timing (losing efficiency and power) to prevent pinging. I dont think Harley's have knock sensors so that is probably why they recommend 91 octane -- to avoid detonation.

Therefore it's 91 or higher octane for me.....also it costs nothing compared to the value of the scoot.

May 20, 2011 | 03:30 PM

#43

strtarrow

Banned

Joined: Feb 2009

Posts: 6,259

Likes: 5

From: NW NC

Rumor, myth, whatever. The fact is HD recommends 91 as a minimum. I used to prefer Shell or BP because of the additives but as of late started running whatever stations have a separate hose for each grade. I wish there were still Sunoco stations that had 94 octane as I would go out of my way to get it. Ya spend big bucks on your bike but run a lesser octane rating than HD suggests????

:icon_ fryingpan:

May 20, 2011 | 03:40 PM

#44

lh4x4

Extreme HDF Member

Joined: Dec 2007

Posts: 13,402

Likes: 941

From: Illinois

I have been running regular in my HD's, Corvette's and Viper for years. Good starting and smooth running. No trouble with knocking as I don't lug them.

All fuel injected vehicles in the US by nanny EPA rules must be able to run on 87 Octane gas. That is why they have knock sensors to retard the spark advance some to prevent knock.

Yes HD's do have knock sensors.

However if one does not do wot takes offs and shifts at a proper rpm, it will not come into play. I can take off aggressively without incurring knock. The lower the gear the less likely it will knock. At higher speed and lower gear with a heavy load then they will knock. The rider has as much or more control to prevent knock as the EMC.

Power is not octane. It is only a measurement of a fuels resistance to ignition. Power in gas is BTU's. A gallon a gas has 115,000 BTU's no matter what octane. Power is the expansion of hot gasses. The lower the octane the more it burns before the exhaust valves open. No gasoline burns completely but the higher the octane the more that goes out the exhaust.

It is more than likely that easier starting, smoother running and a increase in mpg's is possible with 87 octane. You just need to not lug the motor.

Last edited by lh4x4; May 20, 2011 at 03:56 PM.

May 20, 2011 | 03:41 PM

#45

iclick

Extreme HDF Member

Joined: Sep 2005

Posts: 11,615

Likes: 50

From: Baton Rouge, LA

Quote:

Originally Posted by svt_ct

I dont think Harley's have knock sensors...."

Modern Harleys have ion-discharge knock sensing, but I don't know what year this started.

May 20, 2011 | 03:44 PM

#46

FDHOG

Stellar HDF Member

Joined: Jul 2010

Posts: 2,275

Likes: 241

From: Highlands, NJ

Quote:

Originally Posted by Arizona

It's .20 cents difference between regular and Premium. Usually when I stop to fill up it's about 3.5 gallons. That's a .70 cent difference in the price of a fill-up. Not worth worrying about to me. If it was an F350 with dual 30 gallon tanks maybe I'd freak over .20 cents a gallon, but not with the bike.

My F150 has a 30gal tank, but runs great on regular. 13-18mpg

Some guys on this forum crack me up. Riding a $20K+ HD and looking to cheap out over 30 cents a gallon on a ride that gets over 35mpg.

May 20, 2011 | 03:52 PM

#47

dohadex

Road Captain

Joined: Sep 2009

Posts: 718

Likes: 1

From: Panama City, FL

I posted a thread a few months ago asking what everyone was using and/or recommended. Hands down---PREMIUM GAS!

Since gas prices got to be bullshit, I started using the mid-grade...it works fine. Now I am using regular 97 octane gas...STILL runs fine!
Since I have a richer AFR, it keeps it from pinging. I've yet to hear one ping.

Cheers...

Dex

May 20, 2011 | 04:08 PM

#48

lh4x4

Extreme HDF Member

Joined: Dec 2007

Posts: 13,402

Likes: 941

From: Illinois

It is not a question of cost for me. I have more than enough $ to last my lifetime several times over. It has to do with waste which I abhor.

I have ridden my bikes all over this country without ever an issue with regular. So I consider it a winning strategy.

It would be difficult for anyone to argue against success. Even the 103 hp 08 Buell Ulysses XT handled the full load from Illinois to Alaska and back through the Rockies and desert. Ran strong on regular. Same for the 90 hp Xr1200.

The 010 Ultra has done 10K and will add 10K more this season on the Pacific Coast Highway trip from the Canadian border to the Mexican border. All with a full load of supplies and equipment. The 07 FXSTC has run side by side with two different VTX 1800's and stayed right with them. No knocking. Other than put on the break in miles on the Dyna Super Glide it has not done much. But it has only had a diet of regular gas.

So, five bikes tens of thousands of miles and no knocking, broken rings or lands or holed pistons settles the debate for me. I think those that say their bikes knock maybe should learn to operate them better.

Last edited by lh4x4; May 20, 2011 at 04:10 PM.