[itaya]

I need to estimate the dynamic viscosity of a fuel mixture.
The mass fraction of the mixture is 1:13 gasoline to air at 373K which is in a gas state.
I'm having trouble finding the properties of gasoline vapor, is there is a different substance with close properties?
or is there a simple way of calculating the mixture viscosity? or maybe using the properties of air is a good enough approximation?
I can allow an error within ~15%

I will be very happy to read your advice...

[curiouscat]

Temperature? Pressure?

[Borek]

My gut feeling is that properties of air should be good enough (taking into account given mass fraction and 15% error). But I can be wrong.

Technically gasoline is a mixture (and not a well defined one - some of its properties are regulated, but not the exact composition). Its main components are hydrocarbons with 4-12 carbon atoms. See if you can find viscosity of the octane-air (or heptane-air, nonane-air) mixtures - while it will be still only an approximation, it should be a better one than using data for the pure air.