What is the best grade of gas for my 2000 suzuki bandit 1200 s

Check the manual for all these questions. Order one at a Suzuki bike dealer if you do not have one.

conventional 87 89 or 93 , without ethanol if you have it available in your area , the ethanol makes a bike run with less power

l have almost always run premium in my Bikes (currently on a DL1000 suzuki, previosu bike a RF900R suzuki)

Some people will tell you premium is not worth the extra cost, but since gas has hit 3.00 a gallon pretty much every where, what is 20 cents more a gallon? l knwo my DL gets about 4-5 mpg better on premium than it does on Regular.