Bob,
Yes, that can happen.

Some of it has to do with the oil contents, and the breakdown of castor / synthetics. More oil in your fuel means less burnable components.

No two brands of fuel on the market are 100% identical. Oil type and viscosity (hydroxyl) may differ, type of castor, quantities of the above, by weight or by volume blending, type of de-foamers, etc....

Other reasons are the quality of the burnable components and type and amount of any additives.

Every fuel brand, even staying within the same advertised nitro blend will run a bit differently. High and low end needle settings will be different, sometimes only slightly different to make your engine run within its desireable limits.

Different types and quantities of oil and the amount of methanol in the mixture have different effects on internal cooling (how much heat is taken away with the oil molecules and how much heat is absorbed by the methanol and nitro before combustion). Thus, needle settings will differ to keep your engine in its happy spot.

Similar to richining the needle when a higher nitro is used, more fuel will be burned in the same length of time. Every engine acts differently with every fuel, sometimes a lot, sometimes only slightly.

Excelent question Bob.

Fuelman