Starting with the actual definition mileage:
[MASS NOUN]
1.0 A number of miles travelled or covered:
the car is in good condition, considering its mileage
2.0 informal Actual or potential benefit or use to be derived from a situation or event:
ODO
The literal definition refers to a number of miles, while the metaphorical application refers to any benefit. You receive a practical benefit when a horse, a car, a train or a gallon of fuel carries you a certain number of miles. Likewise you receive a benefit when a situation or event "carries" you toward your goals and desires.
We use the word mileage in the metaphorical idiom, get a lot of mileage out of something:
Fig. to get a lot of use from something, as if it were a car.
Bob always got a lot of mileage out of one joke.
I got a lot of mileage out of my TV before it broke down.
From: McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.
When we buy a car, we assume there are a certain number of miles in the car, and we get milage out of the car by filling it with fuel, driving it, and maintaining it properly. The fuel we use, how we drive the car and the way we maintain it will affect how many miles we get out of the car before it ends up in the junk yard, but we literally hope to get a lot of mileage out of the car.
When we fill the tank of a car with fuel , we assume there are a certain number of miles in the fuel tank, and we get mileage out of the tank by driving the car. The design of the car, the fuel we bought, and the way we drive will affect how many miles we get out of the tank, but we literally hope to get a lot of mileage out of the tank.
When we tell a joke , we assume there is a certain amount of laughter in the joke, and we get laughter out of the joke by telling it. The nature of the joke, the mood of the audience, and the way we tell the joke, will affect how much laughter we get out of the joke, but we metaphorically hope to get a lot of mileage out of the joke.
When we do a good deed , we assume there is a certain amount of good will in the deed, and we get good will out of the deed by doing it. The nature of the deed, the people who know about it, and the way we did the deed, will affect how much good will we get out of the deed, but we metaphorically hope to get a lot of mileage out of the good deed.
Although it is significantly less common, the preposition from creates a similar adverbial movement:
But the difference is all in the care of the tire, and provided you
have good tires to start with, failure to get mileage from them in
seven cases out of eight is failure to use horse sense in your driving
and in your care of your equipment.
From Country Life in America, July 1912, Volume 21,
We assume there are a certain number of miles in the tires, and we literally hope to get a lot of mileage from the tires.
Using the preposition by does not change the meaning of the word mileage, but it does change the focus of the idiom. With out of or from, we focus on the movement of a benefit from the item, situation or event. With by, we focus on the means of extracting it:
preposition
[OFTEN WITH VERBAL NOUN] Indicating the means of achieving something:
ODO
Examples of getting mileage in autos, publishing, and painting:
Conclusion:
The idiom get a lot of mileage tends to mean get a lot of benefit regardless of the preposition that follows. The most common expression is get a lot of mileage out of, meaning obtain an amount of benefit from. Get a lot of mileage by usually identifies the means of obtaining that benefit.
Specifically:
"I think you'll obtain benefits by trying this out loud or on
paper."
