I think by high octane he wants you to run like 92-93, not reace gas. 85 is REALLY low for an 11.3:1 motor. I think the minimum octane it calls for on the side of the Z400 is 87. That's still awfully low for 11.3:1, but the manufacturer says it's ok due to the design of the motor.
Running race gas on a stock motor will not add any power, but can aid in protection when jetting is slightly off. I also heard that there is going to be a new fuel coming out just for 4 strokes that will add 3 hp, but costs $8 a gallon. Too deep for my pockets!
I would recommend not using anything less than 93 octane. It will not improve power, but in the long run it will help with reliability and help to possibly prevent break down and premature wear. The lower octane isn't bad and you can run with it (I would not run anything lower than 87 octane though).
The dealer told us to run 93 in the raptor, then we read the manual and it said anything higher then 86 so we just run 87 and its fine. Higher the octane will not do anything for stock machines. We have found out that higher octane makes it harder to start cold.
I havn't heard enough good things about octane booster to make me want to use it. 93 octane should be used becuase this is a high-performance machine. Its like running 87 in a Ferrari, its just not right. The Raptor might be fine with 87 cuz its liquid cooled and i think it has a compression lower than 10. But the Z is 11.3:1 so 93 is good insurance. AS for running 93/race gas, ur wasting ur money, a cooler running motor puts out more horsepower but in a stock engine its a waste and its harder to start.
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