My 07 Ultra runs just fine year round in Phoenix on 87. Bike definitely runs better in cooler weather, but does not ping on any grade of fuel, even in summer. Every time I try a tank of 89 or 91, even in summer, no difference. My mpg goes UP with lower octane fuel especially fall through spring.

Also I did not know as the octane goes up more detergents are added. News to me.

 

Higher Octane fuel burns slower than the regular. Harley tunes your bikes to run on this slower burning fuel to reduce the occurance of knock.

If you switch to a lower octane fuel, you might be causing problems other than knock. Not all pre ignition can be precieved by the rider.

Most modern engines use a knock sensor to dial back timing when knock is identified. Most drivers will never hear this knock as the sensor is much more sensitive to it's occurrence.

It's your bike. Feed it what you wish.

 

I ran the pure unleaded (non ethanol) gas in Sturgis and the 07 Street Glide ran like a champ.

 

Oh, goodie! A fuel thread! Seriously, Bikerlaw has it nailed...the other things to be aware of is one fillup of fuel means nothing...need to do it for a while...the first fillup contains a lot of the fuel that was in there.


I am in the habit of filling with 91 octane higher zoot fuel whenever I have the choice...Chevron with Techron is my first choice then Shell, Mobil, Unocal, and everything else after that...I'll run some Sea Foam thru, and some Startron, just for ducks...but if your bike runs good on the cheap stuff, yeah, do it, I'm not so certain that I, and everybody else running expensive stuff thru our bikes, aren't throwing our money away...


For me, I get peace of mind out of it, just like changing my synthetic oil every three thousand miles. The scientists will tell you that's a waste of money, time, and effort...but then again, I'm not a scientist...

 

I'm filling up my Bimmer with 87 today at lunch. NOT!! I like bikerlaw's post. I know that BMW references the detergents more than they reference the octane.

 

I used to work at a golf course; the mechanic there did an experiment toshow the Superintendent that running super-unleaded was better than regular.They took two brand new lawnmowers and tagged them so on would only run superand the other regular. I don't know the actual times so not going to guess herebut for the purpose of demonstration, the one running regular was toast afterthe expected amount of cycles but the one running super was still going strong.

This could be due to tolerances and inconsistencies in QA but they startedrunning super in all the equipment after that and probably still do to thisday.

 

Not sure where you're getting your information, but factory compression is 9.6 or 9.7:1, not 8.5, BIG difference. Was it a typo on your part?

 

I just put my first tank of regular in to test as well.

 

I have run 89 Octane in my 14 SG like every other tank of Gas, and premium the other
part of the time. Here in Reno Nevada our altitude is mostly 4400 feet above sea level
and can go up form there. Most people are not aware that the higher the altitude the less
Octane an engine requires. As far as to the additives in the gas, Fuel Injected engines,
requires more then our old carbureted engines of the 70's & 80's, that is all I have to say.

 

I stick to 91 (highest available in my region). I never realized this was supposed to be performance related issue but do understand it to be a long term damage issue. Ethanol is hygroscopic (attracts water) so storage with it in your tank isn't good. Ethanol run in air cooled engines, not designed to accommodate the extra heat it generates, is apparently also not a good thing. It doesn't surprise me in the least that those seeking to pose as smarter than the MoCo engineers can burn a tank of 87 Ethanol and cry "Voila" nothing bad happened. IMHO their epiphany misses the point.