I like putting premium in my bike. If they had something better than premium I would probably use that.

 

ALWAYS RUN HIGH OCTANE......don't make me say it again,,low octane can damage your engine,,,Harleys are set for high octane,,so you need to run high octane,,,DAMN,,I said it again........

 

I am always amazed at the responses when this question comes up. I love my bike enough to run the best fluids and therefore run the best fuel I can get. Call it peace of mind if nothing else.

 

Octane requirement really does drop with altitude, it's a legitimate question.

 

There is no such thing as "premium" gasoline. It is a marketing thing. All gas has the same BTU's which is where the power comes from in an internal combustion engine.

Octane is simply a measurement unit of a blend of gasoline to resist ignition.

The power comes from the gas expansion when ignited. So the cooler the incoming charge the more expansion. The fuller the amount of fuel burned increases the expansion. No gas burns completely and the unburned goes out the exhaust port. The lower the octane the more fully it burns. There are some riders who are very alert have noticed that lower octane gas in their air cooled engines runs hotter. It will also provide a slight uptick in mpg.

87 octane will start better. Old school mechanics back in the 50's to 70's before FI would run lower octane in the winter for better starting. They would also retard the spark some.

The higher the octane the more goes out the pipe unburned.

91 octane for a HD is the "recommended" gas to use. The ECM will allow the use of 87 octane not because HD wants to but because they are required to by the government.

If you try to go from Denver up to the Eisenhower Tunnel at about 12,000 feet elevation with 93 octane you will be blowing huge black smoke and your bike would stall at idle.

Again power is the expansion of hot gasses not octane.

 

Would you do it? If the answer is yes, then why? It saves you literally pocket change and the downside far outweighs any minimal savings. If not to save a buck, and I'm being generous, what other reason is there for doing it if you have a choice?

 

alot depends on year of bike 07 is a ping crazy monster when stock.ive had to run 89 ping more but it was controlable with proper gear selection.so at elevation it shouldnt be a problem.06 is one of the hardest years to get a ping. its in the tuning wich is different year to year.and as said in a previous post if u are aware of ping and how to control it no problem.

 

i moved to oklahoma from colorado about 9 years ago. a big difference in altitude, 5,000 ft to maybe 800 if that. during my last trip to colorado i drove my late model corvette and stopped by the corvette shop in colorado springs to visit with my friends there. they gave me a leaflet as to why premium isn't needed at high altitude. the basics is that there is much less air to compress, so my 11:1 compression ratio was more like 8.5:1. that's how you can very easily get by with using 87 or 89 octane at high altitudes. and it works. now down at lower altitudes there's a lot more air to compact with each compression stroke, so the higher octane is needed, but not at high altitudes, the air is so thin that there's not much of it to compress with each stroke.

 

If 87 octane is sufficient, then why would MOCO recommend 91 octane???

 

The lower octane fuel will make slightly more power if you're not getting into knock at all. That's reason enough besides the fuel savings. If I lived above 5000 ft I probably would run 89 all the time.

Again, I'd drive around a bit and log data to verify it, but I definitely wouldn't expect to run into any issues.

If I was really cheap and after each penny I'd use my TTS to retard the spark a couple degrees everywhere, and then I could run 87 even at sea level.