No I'm not thinking of making gasoline at home , but due to improvements  in my stock motor ,such as a tuned intake, and Dyna muffler etc.  I've been thinking of trying 89 over 87 octane gas to see if performance or an increase in mileage might be obtained, at reasonable cost,  and the best way to achieve it.
       The fuel in my neck of the woods, is 87E10 , 89E10, and 91 straight gas. Most of the fuel sold is 87 and 91 , I don't really know anyone that uses 89 , It seems to be the "orphan" in the group and that scares me as this fuel must sit around a long time and has a much better chance of the alcohol picking up water, and the fact that it is an E10 gas and still has only 95% of the energy of straight gas due to the fact that alcohol has only half the energy when burned. It got me thinking there might be a better route to obtaining a better product.
     IF the spread of cost is fairly even between the three fuels (haven't checked)  by mixing 87 and 91 octane fuel ,half and half , (at the pump) there might be gains in the quality of fuel. Octane would remain the same 89 but the fuel would under go a change that of being 89E5 rather than 89E10 it would now contain 97.5% rather than 95% gas and only 2.5% alcohol. A2.5% increase in power and a 50% decrease in alcohol.       DragBikeMike once commented that the DR650 piston ,billed at 10.5:1 may not produce that in the savage ,due to our larger squelch , and I begin to wonder if the fuel I describe above might not work ,gas having a higher combustion temperature than alcohol,  it  might work to ward off detonation.(but I have no way of testing.)
      well anyway ,just another thought from the belfry of the bat

Hotrod, you could well be right,but you could pump the 91 first , and add a little extra. the other thing that may apply in this approach of using 1/2 91 is that the "high priced spread" may have additives that keep your carb /FI cleaner (detergents?) that may not exist in the cheaper fuels.

The octane only serves to prevent detonation.  There isn't any more energy to be had as a result of the higher octane.  If your bike is not detonating on 87 octane, I see no benefit from using a higher octane fuel.  The exception to this would be a modern, computer controlled, fuel injected engine with a knock sensor.  A modern FI engine's control system adjusts timing to achieve best performance.  If you use a higher octane fuel the system will recognize it and adjust timing to suit.

In stock form, our engines check in at about 150 psi cranking pressure.  They don't have enough compression to warrant higher octane fuel.

jcstokes wrote on 01/26/19 at 20:42:24:


The pure gas ages slower than E10 fuel.  The ethanol attracts moisture and phase separation occurs.

The whole idea was based on the fact that my bike might be able to perform better on 89, I have a tuned intake ,that improves VE by  a max. of 4 to 7 % at different rpms throughout all 5 gears ,this may well boost my compression slightly , ( from 8.5 to about 8.78 )and may allow me to actually see an improvement using 89,  and that blending the gas would reduce the amount of alcohol and increase the amount of gas, maximizing it's usefulness . I intend to try it just as an experiment, if I don't see any improvement I'll be going back to E87 as I can't see wasting money. Dave  is correct about the major fuel companies fuel having a better additive package , and I fully intended to use Sunoco for testing.