Does it hurt anything to run the low grade gas in my 06 FLSTI? I have been trying two see what one grade runs better in it and it seems the low grade got the best mileage of them all. Just wondering if this will have an ill effect on the bike if I run this in it. I have been running the low grade then a tank of mid and so on so far and don't seem to be a problem.

 

I only run the high octane. Give the best for your bike. Too much money for the Harley not to.

 

06flsti: What tells you if the gas is not enough octain is detonation or what's known as ping. Preignition is often used in this forum but it's a totally different animal. Glowing carbon or glowing plug tips cause this and it's nasty. Engine life is seconds or minutes at best. Ignition is happening totally independant of the spark and timing and is out of control.
If you are not getting any detonation you are good with your choice of fuel. I would however go up one grade for insurance against detonation. Cold air in a high pressure atmospheric zone could put the lower grade out of usable limits. The higher the octain of the fuel in a given engine, the lower the btu's and slightly less power. MPG will decrease slightly due to this. The highest octain , which is higher than the recommended for your bike is a total waiste of money, with no benifits.
Ron

 

My understanding is you should run the lowest octane possible without pinging. Perhaps someone could elaborate. I run 92 or 93.

 

Donny Petersons explanation:
http://www.heavydutycycles.com/hdgas.htm
Later

 

good article. Thx!

 

Thank you all for the info. I will stick with mid grade just for insurance!!!!

 

mid grade is only 89, right? did you read http://www.heavydutycycles.com/hdgas.htm

 

I know for the 2007 model year and up, HD is recommending 91 as a minimum. I prefere to use chevron gasoline and so far have not had any problems in either my Sporty when i had it, or my current fatboy.

 

When I got my bike, I was told to run Premium. You spend good money on a HD, why not put the best possible gas in it?