If the stuff coming out of the pump is really premium fuel, then there so be no effect from adding the octane booster. All fuel has the same energy content, regardless of octane. The energy of all automotove gasolines is around 115,000 BTUs per gallon. Diesel fuel has around 130,000 BTUs per gallon.

An octane rating of 91 means that the fuel has the same resistance to burning upon compression than a fuel with a mixture of 91% Octane and 9% heptane.

The only way that a higher octane fuel would make a difference is if the fuel in the tank is of too low of an octane and the engine is having to retard the timing to prevent detonation and thus the power loss.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record