I profile gas stations, if they look like crap the gas is probably crap too.

Check out yer HD manual for your year of bike - the min Octane recommended is 87 - but I only 92 or 93 octane in mine. If your on a road trip and 87 is all you can find then it won't hurt to use it but I would be looking for 93 for the next tank.
Another advantge of using hi-octane is it burns cleaner and doesn't leave carbon build up on the valves and heads; the reason for this complete burning of the fuel.

Shells premium V-pro, even found it w/out ethanol.

Most pumps in Mn have 91-93 octane nonoxygenated(no ethanol) for "collector cars small engines, motorcycles, etc".It's what I use in everything but my car and pickup.

The manual for my '03 Dyna (twin cam 88) says to use a minimum of 91 octane, I wouldnt use anything less than that unless your manual states otherwise.

I run 91 because that's the highest they seem to sell in the Bay area.

Must be OK because there arent any pings.

i have been looking for any un-mixed fuels here in texas, no luck, i add octane boost to help kill the pre ignition

Always use premuim Sunoco 93 when I can

Octane is a retarder as previously mentioned. High compression and high heat will cause the fuel to ignite prematurely, putting extreme stres on the engine by exploding while the piston is still compressing. When my bike was an 883, I used 87 and it ran fine. Now after the 1200 conversion and high compression mods, 87 will sound like a drum solo on a tin cup. Octane keeps the fuel stable until it gets ignited by the extreme high heat of the arc on the sparkplug instead of the moderately (in comparison) high heat of the cylinder walls and lowering of the fuels flashpoint via high compression.

This is why diesel fuel is used in diesel engines, it resists ignition well past the compression generated by a gasoline engine and then is ignited by pressure alone. you could never get to full operating pressure with gas in a diesel because it would ignite way too early. This high compression is why diesels have so much torque at low RPM.

Bottom line, if it's not pinging, you don't need higher octane. If it's pinging....you do

Almostforgot.....most of the carbon build up is from running too rich a mixture. you can drill out the EPA plug on carbs and adjust the idle mixture screw (it's a crime LOL) to lean it up a bit. you can also rejet the carb. The idle mixture screw (Not the idle speed setting screw) and jets control fuel flow at different rpm's. My Sporty has Keihnin CV for instance. It's got the Idl mix screw, a slow jet and a fast jet. Obviously the idle mixture is for idle fuel supply only, then mid range is suplied fuel by the idle mixture orifice and the slow jet orifice, then high range throttling uses the fast jet/slowjet/idle jet to supply fuel. So each jet has a range it kicks in and is then in use until you come back down below it's range of use. with an air/fuel meter, you have to inspect the plugs. this is a seat of the pants art form and I can't write a book here but, broken down, if your plugs are clean or have ligt brown to white soot on them; your too lean and need to increase (enrichen) your air/fuel mixture. Black soot is too rich (if it's on the plugs, it's on everything else too). You should be looking for a medium brown residue on the plug. Keep in mind, you may have the correct idle mixture settingand slow jet sooting that may be masking a fast jet lean problem as the high rpm dwell time may not b enough to burn off the correct brown soot from the lower ranges to reveal the too lean condition off the fast jet. It takes a lot of plug cleaning and re-running to get it dialed in. there will be times i will take a clean set of plugs in my pocket out to a country road, install them and immediately go balls to the wall to soot them up and then kill the engine before stopping so i don't screw up the fast jet sooting so i can see what i'm getting at high throttle settings without the idleand slow jets leaving their mark on the test plugs.....Did i mentin i get a little OCD about some things.

I have always just used what the manufacturer has called for. Never have I had a fuel related problem in either auto or motor. Currently...since 1984, last Harley...use 87. The last time I saw Ethyl was when I was putting around in a 67 Goat, I do miss the both of them. Oh, auto or motor...very strict about maintenance schedule and quality of products used.

The one thing I tell people about Octane... it doesn't give you improved performance, it helps protect your motor and keeps it running in its original manufactored condition, or as close to it as possible. If you want performance then you have to add and subtract engine components and go through tuning via Dynomometer.
Honestly, all the bikes being manufactured today are suppose to meet a strict emissions guideline and motorcycles are becoming more and more tamper proof with catilytic converters, sensor technology and these new valves (for all you Harley Riders) that create way more torque than horsepower because they don't open during the exhaust portion of the 4 stroke compression process.
The EPA demanded it of the car companies and it was only a matter of time before they got to us!

I know there are still some fuel vendors in TX with unpolluted fuel.  I've seen them, just can't remember off the top of my head  who it is.  Must be gettin old. 

I've always used 91-92 in my old shovelhead, and was wondering what I was supposed to use in my new Ultra Classic.

Thanks!

Hypno, You should be running 91 or 92 octane in the new bike as well. I believe the HD owners manual calls for 91.

Like most folks so far I run 91 (93 as 91 is not availabe but at a few stations around here Mass.) This is what Harley calls out for in there twin cam engines. The one thing to watch for is the ethanol mix in the fuel. Presently a twin cam harley can take 10% mix of ethanol and 90% gas. Some are starting to play with 15% ethanol which i'm not sure how well it will take to.

Thanks BailOut - That is what I am getting from the discussion. I tried the gas that is one step down from premium and she started rattling. So you all are definitely right.

Alright, I'll throw in my 2 cents, and keep it short on tech stuff, since there's been plenty of good input.... On the bike, I use mid-grade, and have noticed a decent boost in milage from when I use regular. However, in my truck and van, I do something a little different... I do put 87 octane in, but for every 5 gallons, I add 1 napthalene moth ball. This does several things, including but not limited to (lol) boosting octane into the 90's, cleaning carbon deposits in the cylinders, cleaning carb jets and fuel lines, removing water (from condensation) from the system, and acting as an fuel anti-freeze. I have been doing this since I started driving, learned it from my Dad, who I believe learned it from an old stock car racer. I've NEVER had one of my old carb-run vehicles fail to start in cold weather, I get excellent longevity from my spark plugs, and over-all, my old trucks run very well and have above average fuel economy.

I have to say that this WILL NOT WORK if your car, truck, or bike is equiped with a catalytic converter. The harmful carbon deposits that the solution takes care of comes out in a black stringy substance that is not a problem for your exhaust system, but will foul up a cat if you make a practice of it, and that's an expensive mistake. (of course, they're worthless, and if your area doesn't have emisions testing, I'd take the thing out and replace it with a small peice of flex pipe)!

To be back on topic, if you have a newer vehicle, the best rule is to follow the owner's guidelines, I know for a fact that not all modern engines can tolerate good gas; for example, I know someone who managed to blow up on the early PT Cruiser by putting 93 octane in it. The aluminum cyclinders softened too much from the heat, and it was cooked. (at least that's what the dealership mechanic told him when he tried to turn it in for warranty work!) Follow the instructions, and you should be in good shape.

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What is important right now is that, you are smarter and wise in choosing the right one and the best thing that you deserve.  Even though there are so many brands and offerings in the market, still you are looking for the best quality that you can rely on.  So that you can feel all the confidence while you are driving on your way.