I typically run 91 or 92 octane without corn.
A local station carries it, but the valving at the pump I am sure leaves me getting some 87 with corn for the 1st gallon or so.

Yesterday I had a chance to put some 100 unleaded in her, and what a difference. I run stock compression with a decently tuned stage 1.

I noticed before when riding 2 up, at 65 - 70 mph, 238 degrees, if I pin it I could get a little rattle from the top, and with the 100 its gone. I wont be filling with $8.25 per gallon very often but, I will be topping off with octane booster from here on out.

It was more for curiosity I did this (one of the guys in our group has a 127" Road King at 10.5:1 or 11:1 so needs the higher test) and he had to stop and fill so I just filled on a whim. I needed 4.6 gallons so the majority should have averaged up pretty good. I am going to go beat on it a little bit today (solo) and see if I notice a difference in any other way.

Just one of those things that make me go, hummmm.....

 

Try finding a station that does not use a mixer pump for the premium. That way you will not get that 87 for the first gallon or so like you mention.

 

What octane rating would 90 pure gas be as compared to 93 octane with 10% corn? My Trike was tuned on 93 and we now have a station close by the sells 90 octane pure gas. Just wondering if trying some will ruin my tune.

 

Was the 100 race gas or avgas? Avgas is labeled 100LL. LL means low lead but it has a good bit of lead, prolly way more than a cat can stand but if you don't have a cat avgas runs under 6 bucks normally.

 

Theres WAY less than a gallon left in the hose......more like a cup or two. Octane boost is a huge waste of money. They typically raise the octane 1 point. So if you normally pump 92 the octane boost will raise it to 92.1.

 

Also, higher octane fuels have less energy per gallon. Less energy = less power. If you use the octane level fuel your engine was designed for and your engine is detonating theres something wrong with your engine.

 

Higher octane burns slower, thats why high compression engines need it or they would pre detonate all the time and ruin the engine, you should use the lowest octane possible with no pinging for the most power, my carb tuner for my race car taught me about gas and octane, even in my race car I mix a little 87 octane, he has found it makes more power that way, in a 5 gallon jug of 110 race gas I will put about a half a gallon of regular 87 octane gas in it. In my 650 hp race motor I get a few more ponies doing it that way, he told me the 87 has more oxygen in the fuel.

 

Presuming an honest rating, 93 octane is 93 octane no matter the corn content. The viscosity of 20-50 dino oil should be the same as 20-50 synthetic again presuming an honest rating.

Where you may be getting confused is that 90 octane pure gas can get a higher octane rating with ethanol mixed in, but so can a mix of 90 and 95 octane pure gas be rated above 90 based on the proportion of the mix. Either your machine can tolerate 90 octane (regardless of corn content) or it can't. I have found mine is tolerant of mid grade where I live so that is what I use. I am fortunate to still have pure gas as an option. The only time mine gets corn is on a trip when there is no option.

"Tune" is timing and mixture set into the computer which can be adjusted slightly by O2 sensors, temp, atmospheric pressure. The grade of gas you use will not change the data load in the computer so there is no "ruining" your tune. If you get poor enough gas, there may be damage to the hardware of the engine caused by pinging, detonation, and deposits. If it is severe enough or lasts long enough it can crack pistons, burn holes in them, damage bearings, foul spark plugs BUT it won't ruin your tune. If your O2 sensors get fouled, they will no longer provide data to the computer to optimize the current situation, but again, the basic data load will remain unchanged.

The computer has a control function with very little feed back, though there is some. It is much like a light switch. The light switch turns the electricity on and off, it doesn't care if the bulb is burned out or not. The "tune" of the light switch doesn't change based on the condition of the light bulb.

 

If your running 91 to 92 octane in a stock harley motor and your still pinging then you got something going on with your tune. Running a 110 octane in a stock bike motor is a waste and those octane booster are snake oil. You should be able to run 92 all day long. IMHO

 

For all but the hottest days in the summer I can run 89 octane with zero problems in both my V-Rod and Ultra. The ultra I run 89 year round, and have yet to have it ping. The V-Rod will ping on days in the upper 90's while hot, like in stop and go traffic.