I get better milage with 87 octane then 93 octane. One bike is a 04 with 95" kit in it and the other is a 07 with a 96" engine in it.

 

Running Hi Test in a motor not requiring it will foul the plugs, the gas does not burn fully.

 

That's a new one to me. I know running too rich or worn out rings will foul your plugs. I have a drum of VP Racing gas (107 octane) that I use in my Porsche Cup car. Tried it in my bike, no difference from Sunoco Ultra.

 

What I've seen is that running too high an octane will cause more deposits in the combustion chamber for the reason stated - fuel doesn't completely burn. But that doesn't necessarily happen as much as it used to because of the additive levels in some brands, and because modern electronic ignition systems (ones with knock detection) will advance the timing to the point just before detonation/preignition occurs, and where the fuel burns more completely.

Many moons ago during Shovel & Ironhead days most of us ran premium. To not run it was unthinkable 'cause you would get pinging as soon as you hit the throttle a bit more than usual. Plus the hemi-head design of those engines made for crappy ignition as the piston dome effectively blocked the flame path. When I rebuilt the top end on my Shovel I put in 6.5:1 CR pistons. I could pretty much run melted peanut butter for gas after that. Didn't bother me too much in the performance 'cause we're talking about a bike with a 3 speed/reverse transmission; it wasn't a hot rod.

For those who run octane booster, check out how much you have to add to increase the octane an appreciable (noticeable to your engine) amount. Too often they are just little bottles designed to take your money.

Choose your poison, watch for results, and just ride. If you are alert enough to not be a hazard to yourself and others on a bike, you'll know when your bike is happy, and when you've managed to **** it off.

 

I use only 93 oct, some only have 92 and it seems ok..

 

cheap and most octane boosters are just toluline which is not great for engines also this is what most fuel system cleaners contain. check with most good engine builders

 

You'll find that in the higher altitudes you can run a bit lower octane w/o any problems.

 

Isn't the green button Diesel?

 

I'm with you on that one. High octane fuel has a lower flash point than low octane does. My Road KIng Classic owners manual recommends 91. Unfortunately, I can only get 92 octane in my area.

 

Imagine putting Diesel in your tank by accident. Opps! ROFLMAF