What fuel grade in my f4i. Thanks. What does the book call for.

 

87

 

but if you want to waste money and gas so you can make your bike less powerful as well as accelerating the corrosion of your exhaust system, then run 91. The ladies love it when you tell them that you're running 91.

 

Specs say 91 minimum. I run 93 with no ethanol.

 

Tried 87 on my bike bone stock got 20 miles less per tank, took longer to start and
with 92 the throttle responds smoother so 60 cents a tank i'll take 92.

 

Obvisiosly you don't have an F4i.
Weird, it is usually the other way around, Could be you were riding differently?

 

the only person i know who says running a higher octane gives a higher gas millage, i don't believe, he's that kind of person.
Run what is reccomended or lower if you can, the higher the octane the more STABLE the gas is, meaning it doesnt blow up as quick, it burns slower, builds up more carbon.
run a higher octane gas if you experience detonation, when the fuel ignites before its supposed to.
higher never meant better. its about the compression ratio.
also jets run on kerosene.

 

Something to keep in mind is that different octanes are available in different regions based on elevation. In Utah, premium gas is a lower octane than premium along the coast. This is done because of how the fuel burns at different elevations (air pressure, oxygen level, etc).

That being said, I run mid-grade. I haven't noticed any power difference between that and premium, but I do get slightly better mileage. Better mileage means you're getting more power out of the gas (per x amount), and getting more power out of the gas means it's burning more completely and leaving your engine cleaner.

 

To add a little bit:
Higher octane requires more heat to combust (which is why it's more stable). Engines with higher compression ratios can run on higher octane gas because pressure = heat. When a higher compression engine runs a lower octane (less stable) gas, the heat generated by the compression ignites the fuel before the spark plug does. This is detonation, and is what causes the "ping" sound when you're not running high enough octane.

 

You should never run lower than recommended.