Oil in gas tank?

[mechtech2]

Even if the mileage remains the same, I use 2 stroke oil primarily for the fuel pump with alcohol infused gas.
Nice to have a bit of top end lube, too.

 

[randomhero439]

UPDATE Civic:
Benchmark (no oil), 1586 miles, averaged 28.9mpg ~ 70-80% city driving.

Fill up 1: 29.4mpg, 76% city driving, 1:500 ratio
Fill up 2: 30.5mpg, 89% city driving, 1:640 ratio
Fill up 3: 30.0mpg, 88% city driving, 1:640 ratio
Current average over 903 miles: 29.9mpg (3.5% gain in mpg)