Jump off the soap box, the guy asked a legitimate question.

 

As suggested, if your bike runs ok on 87 octane, no harm in using it. My last bike didn't like 87. In fact it didn't like 89, it loved 93. Of course there were a few mods involved in that one

 

Try regular for a few tanks, then report back on your findings.

 

Owners manual says Recommended not Required. Its your bike if you want to run 89, 87, what ever. Let us know how it works out. Some have done it and said it ran fine. Others say it did not. Every bike is different. Good Luck

 

The need for octane is based on heat and many have pointed out that an air cooled engine is not as well temperature controlled as a liquid cooled engine. Compression itself also generates heat and you live close to sea level. That means you live where the air is dense and you get more air per intake stroke than someone living in Denver, hence more heat build on each compression stroke. In Oklahoma, at 1300 feet above sea level, mid grade works well for me in a 2008 96 ci stock Road King. One tank of lower octane won't destroy your engine, try mid grade and see what happens. Some recommend running the tank down pretty low and adding just a gallon or 2 of what ever you want to try. If it causes trouble, then top off with premium and the trouble will be short lived.

Many look at the extra cost per fill up and disregard the difference. I buy gas over a lifetime and a dollar per tank full adds up over time. I am with you, why buy more octane than you need?

 

I find that most of the 91 in my area is non ethanol. That's enough for me to use it. And the manual says to use it, so I use it.
I've put 87 in by mistake a few times in my life. Bike seemed none the worse for it.

 

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9.6 comp isnt real high but it's not as low as you think it is either.

Low comp for a street motor would be in the 8.5/8.75/9.0 compression range.

There's more to octane requirement then just comp ratio like for example cyl pressure thats directly affected by cam timing (Duration vs LSA-lobe separation angle) .

Timing curve,fuel calibration ,load on the motor (gearing & wt being carried/moved) ,heat ,combustion chamber -head-piston design & more all have an affect on what the lowest octane requirement is for a motor to not detonate.

With that said stock cam timing from the factory is pretty mild/short which leads to higher cyl pressure which can make 9.6 comp detonate even on hd's rec 91 octane on hot days esp when you get some miles & carbon buildup in the combustion chambers.

Think about this,yrs ago V8 motors with fairly mild cam timing with an approx 0.5 point higher compression @ 10.0 from gm had red tags in the interior of the new cars from the factory stating they had to run a min of 98 octane fuel to avoid detonation.

So unless you install a cam with considerably more cam timing in your hD to reduce cyl pressure/comp a bit i'd not rec running 87 or 89 octane fuel on a reg basis to avoid damage from detonation.

My HD's stock 9.6 comp 96" motor with 25k miles stopped detonating on on HD's rec 91 octane fuel when i installed an oil cooler with twin cooling fans along with wards cooling fans that collectively together reduced oil temp 50 deg f in summer heat.

But before cooling the motor oil 50 deg f it would detonate often in temps above 60-65deg f on hd's rec 91 octane fuel and had to run 93 octane fuel most of the time to avoid detonation.

I also run a dose of techron thru the motor just prior to each oil change to keep combustion chambers clear or excess carbon buildup along with keeping fuel injectors clean at the same time too .

Doing that reduces a motors tendency to detonate by reducing carbon buildup that in some cases increases compression which also creating carbon hot spots both of which can cause detonation.

Note:guys running loud ex/pipes & or loud stereo may not be able to hear detonation when trying lower grade fuel that over enough time and right cond can do a lot of damage breaking/cracking piston skirts & or the complete piston etc leading to complete engine failure.

I have seen that type damage 1st hand when rebuilding motors for guys that trashed them due to detonation when not running enough octane in their street motors that detonated under load cracking/breaking a piston or pistons also poundng rod & main bearings to death too!

But in a pinch if 87 or 89 octane fuel is all thats avail on a trip when fueling up out in the boonies it would be the only time i'd run cheap low grade / low octane 87 or 89 fuel in an HD that cost's $25,000-30,000 new only because i had too!

And i'd sure try to take it easy on the bike/motor if/when doing that too.

GEESH!!!/LOL!

Happy motoring.

Scott

 

But....but....lh4X4 has put more than 5 million miles on umpteen models of Harleys using 87 octane corn gas with no problems whatsoever - all while getting an average of 76.5467 mpg!

Hard to argue with those results

 

That's what I keep saying. If you are that worried about the cost to fill up a 5-6 gallon gas, go buy a Honda.